HK1261530B - Optical filter - Google Patents

Description

Optical filters

background

Optical sensor devices can be used to capture information. For example, an optical sensor device can capture information related to a set of electromagnetic frequencies. The optical sensor device can include a set of sensor elements (e.g., optical sensors, spectral sensors, and/or image sensors) that capture information. For example, an array of sensor elements can be used to capture information related to multiple frequencies. In one example, the array of sensor elements can be used to capture information about a specific spectral range (e.g., a spectral range from approximately 1100 nanometers (nm) to approximately 2000 nm, another spectral range with a center wavelength of approximately 1550 nm, etc.). The sensor elements in the sensor element array can be associated with a filter. The filter can include a passband associated with light of a first spectral range that is transmitted to the sensor element. The filter can be associated with a filter that blocks light of a second spectral range from being transmitted to the sensor element.

Overview

(1) A bandpass filter may include a set of layers. The set of layers may include a first subset of layers. The first subset of layers may include germanium hydride (Ge:H) having a first refractive index. The set of layers may include a second subset of layers. The second subset of layers may include a material having a second refractive index. The second refractive index may be less than the first refractive index.

(2) The bandpass filter as described in (1), wherein the material includes at least one of the following: silicon dioxide (SiO ₂ ) material, aluminum oxide (Al ₂ O ₃ ) material, titanium dioxide (TiO ₂ ) material, niobium pentoxide (Nb ₂ O ₅ ) material, tantalum pentoxide (Ta ₂ O ₅ ) material, or magnesium fluoride (MgF ₂ ) material.

(3) The bandpass filter of (1), wherein the first subset of layers is a high refractive index layer (H) and the second subset of layers is a low refractive index layer (L); and wherein the set of layers is arranged in at least one of the following: (HL) _m order, (HL) _m -H order, (LH) _m order, or L-(HL) _m order, where m is the number of alternating H and L layers.

(4) The bandpass filter of (1), wherein the set of layers is configured to pass light in a threshold portion associated with a spectral range between approximately 1100 nanometers (nm) and 2000 nm.

(5) The bandpass filter of (1), wherein the set of layers is configured to pass light in a threshold portion associated with a spectral range between approximately 1400 nanometers (nm) and 2000 nm.

(6) The bandpass filter of (1), wherein the set of layers is configured to pass light in a threshold portion associated with a spectral range having a center wavelength of approximately 1550 nanometers.

(7) The bandpass filter of (1), wherein the first refractive index is greater than about 3.8 at a wavelength of about 1550 nanometers.

(8) The bandpass filter according to (1), wherein the first refractive index is approximately 4.2 at a wavelength of approximately 1550 nanometers.

(9) The bandpass filter of (1), wherein the first subset of layers is associated with an extinction coefficient of less than about 0.01 at a particular spectral range.

(10) The bandpass filter of (1), wherein the second refractive index is less than 3 in a spectral range of about 1100 nanometers (nm) to about 2000 nm.

(11) The bandpass filter of (1), wherein the center wavelength of the spectral range varies by less than 40 nanometers for angles of incidence ranging from 0 degrees to 40 degrees.

(12) The bandpass filter of (1), wherein the center wavelength of the spectral range varies by less than 30 nanometers for angles of incidence ranging from 0 degrees to 40 degrees.

(13) The bandpass filter of (1), wherein the center wavelength of the spectral range varies by less than 20 nanometers for angles of incidence ranging from 0 degrees to 30 degrees.

(14) The bandpass filter of (1), wherein the center wavelength of the spectral range varies by less than 10 nanometers for angles of incidence ranging from 0 degrees to 20 degrees.

(15) An optical filter may include a substrate. The optical filter may include a set of alternating high refractive index layers and low refractive index layers disposed on the substrate to filter incident light. The optical filter may be configured to pass a first portion of the incident light within a spectral range having a center wavelength of approximately 1550 nanometers (nm) and reflect a second portion of the incident light that is not within the spectral range. The high refractive index layer may be germanium hydride (Ge:H). The low refractive index layer may be silicon dioxide (SiO ₂ ).

(16) The optical filter according to (15), wherein the high refractive index layer is deposited using a sputtering process.

(17) The optical filter according to (15), wherein the high refractive index layer is annealed.

(18) An optical system may include an optical filter configured to filter an input optical signal and provide a filtered input optical signal. The input optical signal may include light from a first light source and light from a second light source. The optical filter may include a set of dielectric thin film layers. The set of dielectric thin film layers may include a first subset of layers of germanium hydride having a first refractive index. The set of dielectric thin film layers may include a second subset of layers of a material having a second refractive index less than the first refractive index. The filtered input optical signal may include light from the second light source having a reduced intensity relative to the input optical signal. The optical system may include an optical sensor configured to receive the filtered input optical signal and provide an output electrical signal.

(19) The optical system according to (18), wherein the optical filter is provided on a sensor element array of the optical sensor.

(20) The optical system according to (18), wherein the optical filter is separated from the optical sensor by a free space.

BRIEF DESCRIPTION OF THE DRAWINGS

1A-1C are overview diagrams of example implementations described herein;

FIG2 is a diagram of a germanium hydride-based optical filter described herein;

FIG3 is a diagram of a system for fabricating the germanium hydride-based optical filters described herein;

4A-4D are graphs of characteristics associated with germanium hydride-based optical filters described herein; and

5A-5C are graphs of characteristics associated with germanium hydride-based optical filters described herein.

Detailed description

The following detailed description of example embodiments refers to the accompanying drawings, in which the same reference numerals in different drawings may identify the same or similar elements.

An optical sensor device may include an array of sensor elements configured to receive light originating from a light source, such as a light emitter, a light bulb, or an ambient light source. The optical sensor device may utilize one or more sensor technologies, such as complementary metal oxide semiconductor (CMOS) technology, charge coupled device (CCD) technology, or the like. The sensor elements (e.g., optical sensors) of the optical sensor device may obtain information (e.g., spectral data) about a set of electromagnetic frequencies. The sensor elements may be indium gallium arsenide (InGaAs)-based sensor elements, silicon germanium (SiGe)-based sensor elements, or the like.

The sensor element can be associated with a filter that filters light directed to the sensor element so that the sensor element can obtain information about electromagnetic frequencies within a specific spectral range. For example, the sensor element can be aligned with a filter having a passband within the following spectral ranges: a spectral range of approximately 1100 nanometers (nm) to approximately 2000 nm, a spectral range of approximately 1500 nm to approximately 1600 nm, a spectral range with a center wavelength of approximately 1550 nm, etc., so that a portion of the light directed to the sensor element is filtered. The filter can include multiple sets of dielectric layers to filter the portion of light. For example, the filter can include a dielectric filter stack of alternating high and low refractive index layers, such as alternating layers of hydrogenated silicon (Si:H or SiH) or germanium (Ge) as the high refractive index material and silicon dioxide (SiO ₂ ) as the low refractive index material. However, using hydrogenated silicon as the high refractive index material for a filter associated with a spectral range with a center wavelength of approximately 1550 nm can result in excessive angular shift (e.g., angular shift greater than a threshold value). Furthermore, using germanium as the high refractive index material may result in less than a threshold transmittance for a passband centered around approximately 1550 nm, such as less than approximately 20% transmittance at a wavelength of approximately 1550 nm.

Some embodiments described herein provide optical filters using germanium hydride (Ge:H or GeH) as a high refractive index material, resulting in an angular shift less than a threshold value. For example, the optical filter can include one or more layers of germanium hydride or annealed germanium hydride and one or more layers of silicon dioxide to provide an angular shift of less than about 100 nm at an incident angle of 45 degrees, an angular shift of less than about 30 nm at an incident angle of 30 degrees, an angular shift of less than about 10 nm at an incident angle of 15 degrees, and so on, for a passband centered around a wavelength of about 1550 nm. In addition, optical filters using germanium hydride and/or annealed germanium hydride can provide a transmittance greater than a threshold level, such as a transmittance greater than about 40%, greater than about 80%, greater than about 85%, and so on, for a passband centered around about 1550 nm. In this manner, some embodiments described herein filter light with an angular shift less than a threshold value and a transmittance greater than a threshold value.

1A-1C are overview diagrams of embodiments 100/100'/100" described herein. As shown in FIG1A , example embodiment 100 includes a sensor system 110. Sensor system 110 can be part of an optical system and can provide an electrical output corresponding to a sensor determination. Sensor system 110 includes an optical filter structure 120 and an optical sensor 140, where optical filter structure 120 includes an optical filter 130. For example, optical filter structure 120 can include optical filter 130 that performs a passband filtering function. In another example, optical filter 130 can be aligned with an array of sensor elements of optical sensor 140.

Although some embodiments described herein may be in the context of an optical filter in a sensor system, the embodiments described herein can be used in another type of system, can be used external to a sensor system, and so on.

As further shown in FIG1A and indicated by reference numeral 150, an input optical signal is directed to the optical filter structure 120. The input optical signal may include, but is not limited to, light associated with a particular spectral range (e.g., a spectral range centered around approximately 1550 nm), such as a spectral range of 1500 nm to 1600 nm, a spectral range of 1100 nm to 2000 nm, and the like. For example, the light emitter may direct the light to the optical sensor 140 to allow the optical sensor 140 to perform measurements of the light. In another example, the light emitter may direct light of another spectral range for another function, such as a testing function, a sensing function, a communication function, and the like.

As further shown in FIG1A and indicated by reference numeral 160, a first portion of the optical signal having a first spectral range is not passed through optical filter 130 and optical filter structure 120. For example, a dielectric filter stack, which may include dielectric thin film layers of high refractive index material and low refractive index material layers of optical filter 130, may cause the first portion of light to be reflected, absorbed, or the like in a first direction. In this case, the first portion of light may be a threshold portion of light incident on optical filter 130 that is not included in the passband of optical filter 130, such as greater than 95% of light that is not within a particular spectral range centered around approximately 1550 nm. As indicated by reference numeral 170, a second portion of the optical signal is passed through optical filter 130 and optical filter structure 120. For example, optical filter 130 may pass a second portion of light having a second spectral range in a second direction toward optical sensor 140. In this case, the second portion of light may be a threshold portion of light incident on optical filter 130 that is within the passband of optical filter 130, such as greater than 50% of light that is incident on optical filter 130 within the spectral range centered around approximately 1550 nm.

1A , based on the second portion of the light signal passed to the optical sensor 140, the optical sensor 140 can provide an output electrical signal 180 to the sensor system 110, for example, for imaging, ambient light sensing, detecting the presence of an object, performing measurements, facilitating communications, etc. In some embodiments, alternative arrangements of the optical filter 130 and the optical sensor 140 can be used. For example, instead of passing the second portion of the light signal in-line with the input light signal, the optical filter 130 can direct the second portion of the light signal in another direction to a differently located optical sensor 140.

As shown in FIG1B , another embodiment 100′ includes a set of sensor elements forming an array of sensor elements integrated into a substrate of an optical filter structure 120. In this case, the optical filter 130 is disposed directly on the substrate. Input light signals 150-1 and 150-2 are received at a plurality of different angles, and first portions 160-1 and 160-2 of the input light signals 150-1 and 150-2 are reflected at a plurality of different angles. In this case, second portions of the input light signals 150-1 and 150-2 are transmitted through the optical filter 130 to the array of sensor elements forming the optical sensor 140, which provides an output electrical signal 180.

As shown in FIG. 1C , another embodiment 100 ″ includes a set of sensor elements forming an array of sensor elements of an optical sensor 140 and separated from an optical filter structure 120 (e.g., separated from free space in an optical system of the free-space optics type). In this case, an optical filter 130 is disposed on the optical filter structure 120. Input optical signals 150-1 and 150-2 are received at the optical filter 130 at a plurality of different angles. First portions 160-1 and 160-2 of the input optical signals 150-1 and 150-2 are reflected, and second portions 170-1 and 170-2 of the input optical signals 150-1 and 150-2 are passed through the optical filter 130 and the optical filter structure 120. Based on receiving the second portions 170-1 and 170-2, the sensor element array provides an output electrical signal 180.

As mentioned above, Figures 1A-1C are provided as examples only. Other examples are possible and may differ from the examples described with respect to Figures 1A-1C.

FIG2 is a diagram of an exemplary optical filter 200. FIG2 shows an example stack of optical filters using germanium hydride as a high refractive index material. As further shown in FIG2, the optical filter 200 includes an optical filter coating portion 210 and a substrate 220.

The optical filter coating portion 210 includes a set of optical filter layers. For example, the optical filter coating portion 210 includes a first set of layers 230-1 to 230-N (N ≥ 1) (e.g., high refractive index layers (H layers)) and a second set of layers 240-1 to 240-(N+1) (e.g., low refractive index layers (L layers)). In some embodiments, the layers 230 and 240 can be arranged in a specific order, such as a (HL) _m (m ≥ 1) order, a (HL) _m -H order, a (LH) _m order, an L-(HL) _m order, etc. For example, as shown, the layers 230 and 240 are arranged in a (HL) _n -H order, where the H layer is disposed at the surface of the optical filter 200 and is immediately adjacent to the surface of the substrate 220. In some embodiments, the optical filter 200 may include one or more other layers, such as one or more protective layers, one or more layers providing one or more other filtering functions (e.g., a blocker, an anti-reflection coating, etc.), etc.

Layer 230 may include a set of germanium hydride layers. In some embodiments, another material may be used for the H layer, such as another material having a refractive index greater than that of the L layer, a refractive index greater than 2.0, a refractive index greater than 3.0, a refractive index greater than 4.0, a refractive index greater than 4.5, a refractive index greater than 4.6, etc., over a specific spectral range (e.g., a spectral range of about 1100 nm to about 2000 nm, a spectral range of about 1400 nm to about 1600 nm, a wavelength of about 1550 nm, etc.). In another example, layer 230 may be selected to include a refractive index of approximately 4.2 at a wavelength of approximately 1550 nm.

In some embodiments, a specific germanium hydride-based material, such as germanium hydride, annealed germanium hydride, etc., can be selected for the H layer 230. In some embodiments, layers 230 and/or 240 can be associated with a specific extinction coefficient (e.g., an extinction coefficient of less than about 0.1, less than about 0.05, less than about 0.01, less than about 0.005, less than about 0.001, less than about 0.0008 at about 1550 nm, etc.) over a specific spectral range (e.g., a spectral range of about 800 nm to about 2300 nm, a spectral range of about 1100 nm to about 2000 nm, a wavelength of about 1550 nm, etc.).

Layer 240 may include a set of silicon dioxide (SiO ₂ ) layers. In some embodiments, another material may be used for the L layer. In some embodiments, a specific material may be selected for L layer 240. For example, layer 240 may include a set of silicon dioxide (SiO ₂ ) layers, a set of aluminum oxide (Al ₂ O ₃ ) layers, a set of titanium dioxide (TiO ₂ ) layers, a set of niobium pentoxide (Nb ₂ O ₅ ) layers, a set of tantalum pentoxide (Ta ₂ O ₅ ) layers, a set of magnesium fluoride (MgF ₂ ) layers, etc. In this case, layer 240 may be selected to include a refractive index lower than the refractive index of layer 230 over a specific spectral range (e.g., a spectral range of approximately 1100 nm to approximately 2000 nm, a spectral range of approximately 1400 nm to approximately 1600 nm, a wavelength of approximately 1550 nm, etc.). For example, layer 240 may be selected to be associated with a refractive index of less than 3 over a particular spectral range (e.g., a spectral range of about 1100 nm to about 2000 nm, a spectral range of about 1400 nm to about 1600 nm, a spectral range of about 800 nm, a wavelength of about 1550 nm, etc.).

In another example, layer 240 can be selected to be associated with a refractive index of less than 2.5 over a particular spectral range (e.g., a spectral range of about 1100 nm to about 2000 nm, a spectral range of about 1400 nm to about 1600 nm, a wavelength of about 1550 nm, etc.). In another example, layer 240 can be selected to be associated with a refractive index of less than 2 over a particular spectral range (e.g., a spectral range of about 1100 nm to about 2000 nm, a spectral range of about 1400 nm to about 1600 nm, a wavelength of about 1550 nm, etc.). In another example, layer 240 can be selected to be associated with a refractive index of less than 1.5 over a particular spectral range (e.g., a spectral range of about 1100 nm to about 2000 nm, a spectral range of about 1400 nm to about 1600 nm, a wavelength of about 1550 nm, etc.). In some embodiments, a particular material may be selected for layer 240 based on the desired width of the out-of-band blocked spectral range, the desired center wavelength shift associated with changes in angle of incidence, and the like.

In some embodiments, the optical filter coating portion 210 can be associated with a specific number m of layers. For example, a germanium hydride-based optical filter can include approximately 20 alternating H and L layers. In another example, the optical filter 200 can be associated with another number of layers, such as a range of 2 to 1000 layers, a range of 4 to 50 layers, etc. In some embodiments, each layer of the optical filter coating portion 210 can be associated with a specific thickness. For example, layers 230 and 240 can each be associated with a thickness between approximately 5 nm and approximately 2000 nm, resulting in the optical filter coating portion 210 being associated with a thickness between approximately 0.2 μm and 100 μm, a thickness between approximately 0.5 μm and 20 μm, etc.

In some embodiments, layers 230 and 240 can be associated with multiple thicknesses, such as a first thickness for layer 230 and a second thickness for layer 240, a first thickness for a first subset of layers 230 and a second thickness for a second subset of layers 230, a first thickness for a first subset of layers 240 and a second thickness for a second subset of layers 240, etc. In such cases, the layer thicknesses and/or the number of layers can be selected based on a set of desired optical properties, such as a desired passband, a desired transmittance, etc. For example, the layer thicknesses and/or the number of layers can be selected to allow the optical filter 200 to be used in a spectral range of approximately 1100 nm to approximately 2000 nm, with a center wavelength of approximately 1550 nm, etc.

In some embodiments, the optical filter coating portion 210 can be fabricated using a sputtering process. For example, the optical filter coating portion 210 can be fabricated using a pulsed magnetron-based sputtering process to sputter alternating layers 230 and 240 onto a glass substrate. In some embodiments, the optical filter coating portion 210 can be associated with relatively low center wavelength shifts with varying angles of incidence. For example, the optical filter coating portion 210 can cause a center wavelength shift of less than approximately 20 nm, less than approximately 15 nm, less than approximately 10 nm, etc., with an angle of incidence varying from 0 degrees to 15 degrees; less than approximately 100 nm, less than approximately 50 nm, less than approximately 30 nm, etc., with an angle of incidence varying from 0 degrees to 30 degrees; less than approximately 200 nm, less than approximately 150 nm, less than approximately 125 nm, less than approximately 100 nm, etc., with an angle of incidence varying from 0 degrees to 45 degrees; and so on.

In some embodiments, the optical filter coating portion 210 is attached to a substrate, such as substrate 220. For example, the optical filter coating portion 210 can be attached to a glass substrate. In some embodiments, the optical filter coating portion 210 can be associated with an incident medium, such as an air medium or a glass medium. In some embodiments, the optical filter 200 can be disposed between a set of prisms.

In some embodiments, an annealing process can be used to fabricate the optical filter coating portion 210. For example, after sputter-depositing layers 230 and 240 on a substrate, the optical filter 200 can be annealed to improve one or more optical properties of the optical filter 200, such as reducing the absorption coefficient of the optical filter 200 relative to another optical filter that has not undergone the annealing process.

As mentioned above, FIG2 is provided only as an example. Other examples are possible and may differ from the example described with respect to FIG2.

FIG. 3 is a diagram of an example 300 of a sputter deposition system for fabricating the germanium hydride-based optical filters described herein.

As shown in FIG3 , example 300 includes a vacuum chamber 310, a substrate 320, a cathode 330, a target 331, a cathode power supply 340, an anode 350, a plasma activation source (PAS) 360, and a PAS power supply 370. Target 331 may include a germanium material. PAS power supply 370 may be used to power PAS 360 and may include a radio frequency (RF) power supply. Cathode power supply 340 may be used to power cathode 330 and may include a pulsed direct current (DC) power supply.

3 , target 331 is sputtered in the presence of hydrogen (H ₂ ) and an inert gas (e.g., argon) to deposit a germanium hydride material as a layer on substrate 320. The inert gas may be provided to the chamber via anode 350 and/or PAS 360. Hydrogen is introduced into vacuum chamber 310 via PAS 360 for hydrogen activation. Additionally or alternatively, cathode 330 may cause hydrogen activation (e.g., in which case hydrogen may be introduced from another portion of vacuum chamber 310) or anode 350 may cause hydrogen activation (e.g., in which case hydrogen may be introduced into vacuum chamber 310 via anode 350). In some embodiments, the hydrogen may be in the form of hydrogen gas, a mixture of hydrogen gas and an inert gas (e.g., argon), or the like. PAS 360 may be located within a threshold proximity of cathode 330, allowing the plasma from PAS 360 and the plasma from cathode 330 to overlap. The use of PAS 360 allows the germanium hydride layer to be deposited at a relatively high deposition rate. In some embodiments, the germanium hydride layer is deposited at a deposition rate of about 0.05 nm/s to about 2.0 nm/s, at a deposition rate of about 0.5 nm/s to about 1.2 nm/s, at a deposition rate of about 0.8 nm/s, or the like.

Although the sputtering process is described herein with respect to a specific geometry and a specific embodiment, other geometries and other embodiments are possible. For example, hydrogen can be injected from another direction, from a gas manifold within a threshold proximity of the cathode 330, etc. Although described herein with respect to different component configurations, different relative concentrations of germanium can also be achieved using different materials, different manufacturing processes, etc.

As mentioned above, FIG3 is provided only as an example. Other examples are possible and may differ from the example described with respect to FIG3.

Figures 4A-4D illustrate examples related to optical filters using germanium hydride as a high refractive index material. Figures 4A-4D illustrate characteristics related to a single-layer film based on germanium hydride.

As shown in Figure 4A, and by chart 400, a filter response showing the transmittance of a group of films 410-1 to 410-5 is provided. Each film 410 can be a single-layer film of approximately 2.5 microns. Film 410-1 is associated with a hydrogen concentration associated with a flow rate of 0 standard cubic centimeters per minute (SCCM). In other words, film 410-1 uses non-germanium hydride. Films 410-2, 410-3, 410-4, and 410-5 are associated with a hydrogen concentration associated with a flow rate of 20 SCCM, 100 SCCM, 160 SCCM, and 200 SCCM. In other words, films 410-2 to 410-5 use germanium hydride with increased hydrogen concentration. In this case, germanium hydride films, such as films 410-2 to 410-5, are associated with increased transmittance relative to non-germanium hydride film 410-1. In this way, utilizing germanium hydride in an optical filter can provide improved transmittance. For example, based on the hydrogen concentration in the germanium hydride film, the germanium hydride film can be associated with a transmittance greater than 20%, greater than 40%, greater than 60%, greater than 80%, greater than 85%, greater than 90%, etc. for a spectral range of 1100nm to 2000nm, a spectral range of 1400nm to 1600nm, a spectral range with a wavelength of 1550nm, etc.

As shown in FIG4B and provided by graph 420, the refractive index and extinction coefficient of film 410 are shown. At a wavelength of 1400 nm, the non-hydrogenated germanium film 410-1 is associated with an extinction coefficient of approximately 0.1, which is greater than the extinction coefficients of the hydrogenated germanium films 410-2, 410-3, and 410-5, which have extinction coefficients of approximately 0.05, approximately 0.005, and approximately 0.002, respectively. Similarly, at a wavelength of 1400 nm, the non-hydrogenated germanium film 410-1 is associated with a refractive index of 4.7, while the hydrogenated germanium films 410-2, 410-3, and 410-5 are associated with refractive indices of 4.6, 4.4, and 4.3, respectively. In this case, hydrogenated germanium films 410-2, 410-3, and 410-5 are associated with a reduced extinction coefficient while maintaining a threshold refractive index (eg, greater than 4.0, greater than 4.2, greater than 4.4, greater than 4.5, etc.).

At a wavelength of 1550 nm, the non-hydrogenated germanium film 410-1 is associated with an extinction coefficient of approximately 0.07, which is greater than the extinction coefficients of the hydrogenated germanium films 410-2, 410-3, and 410-5, which have extinction coefficients of approximately 0.03, approximately 0.003, and approximately 0.001, respectively. Similarly, at a wavelength of 1550 nm, the non-hydrogenated germanium film 410-1 is associated with a refractive index of 4.6, compared to the hydrogenated germanium films 410-2, 410-3, and 410-5, which have refractive indices of 4.4, 4.3, and 4.2, respectively. In this case, the hydrogenated germanium films 410-2, 410-3, and 410-5 are associated with a reduced extinction coefficient while maintaining a threshold refractive index (e.g., greater than 4.0, greater than 4.2, greater than 4.4, etc.).

At a wavelength of 2000 nm, the non-hydrogenated germanium film 410-1 is associated with an extinction coefficient of approximately 0.05, which is greater than the extinction coefficients of the hydrogenated germanium films 410-2, 410-3, and 410-5, which have extinction coefficients of approximately 0.005, approximately 0.0005, and approximately 0.000001, respectively. Similarly, at a wavelength of 1550 nm, the non-hydrogenated germanium film 410-1 is associated with a refractive index of 4.5, compared to the hydrogenated germanium films 410-2, 410-3, and 410-5, which have refractive indices of 4.4, 4.2, and 4.1, respectively. In this case, the hydrogenated germanium films 410-2, 410-3, and 410-5 are associated with a reduced extinction coefficient while maintaining a threshold refractive index (e.g., greater than 3.5, greater than 3.75, greater than 4.0).

4C, the refractive indexes of the germanium hydrogenated film 410-5 and the silicon hydrogenated film 410-6 are provided by cutting through the graph 430. In this case, the refractive index of the germanium hydrogenated film 410-5 is greater than the refractive index of the silicon hydrogenated film 410-6.

4D , and provided with respect to the refractive index and extinction coefficient of the hydrogenated germanium film 410-5 and the annealed hydrogenated germanium film 410-5′, is a graph 440. In this case, applying an annealing process at, for example, approximately 300 degrees Celsius for 60 minutes results in the formation of the annealed hydrogenated germanium film 410-5′, which results in an increase in the refractive index (e.g., to approximately 4.3) and a decrease in the extinction coefficient (e.g., to approximately 0.0006) relative to the hydrogenated germanium film 410-5 over a spectral range having a central wavelength of approximately 1550 nm, thereby reducing angular deviation and improving transmittance.

As mentioned above, Figures 4A-4D are provided as examples only. Other examples are possible and may differ from the examples described with respect to Figures 4A-4D.

5A to 5C are characteristic diagrams related to optical filters. Figs. 5A to 5C show characteristics related to bandpass filters.

As shown in FIG5A and via graph 500, a filter response for a hydrogenated germanium optical filter 510 is provided. Optical filter 510 can include alternating layers of hydrogenated germanium and silicon dioxide. In some embodiments, optical filter 510 can be associated with a thickness of approximately 5.6 μm and can be associated with a passband centered at approximately 1550 nm for an angle of incidence of 0 degrees. Furthermore, optical filter 510 is associated with a transmittance greater than a threshold amount (e.g., greater than approximately 90%) for angles of incidence from 0 degrees to 40 degrees.

As shown in FIG5B and via graph 520, a filter response for a hydrogenated silicon based optical filter 530 is provided. Optical filter 530 may include alternating layers of hydrogenated silicon and silicon dioxide. In some embodiments, optical filter 530 may be associated with a thickness of approximately 5.9 micrometers (μm) and may be associated with a passband centered at approximately 1550 nm for an angle of incidence of 0 degrees.

As shown in FIG5C and by graph 540, optical filter 530 (Si:H) is associated with a reduced angular shift relative to optical filter 510 (Si:Ge) for angles of incidence varying from 0 to approximately 40 degrees. For example, optical filter 510 is associated with a center wavelength shift of, for example, less than approximately 5 nm at an angle of incidence of approximately 0-10 degrees, less than approximately 4 nm at an angle of incidence of approximately 0-10 degrees, less than approximately 3 nm at an angle of incidence of approximately 0-10 degrees, less than approximately 2 nm at an angle of incidence of approximately 0-10 degrees, etc. Similarly, optical filter 510 is associated with a center wavelength shift of, for example, less than approximately 15 nm at an angle of incidence of 10-20 degrees, less than approximately 10 nm at an angle of incidence of 10-20 degrees, less than approximately 9 nm at an angle of incidence of 10-20 degrees, less than approximately 8 nm at an angle of incidence of 10-20 degrees, etc.

Similarly, the optical filter 510 is associated with, for example, a variation in center wavelength of less than about 8 nm at a 20 degree angle of incidence, less than about 9 nm at a 20 degree angle of incidence, less than about 30 nm at a 20-30 degree angle of incidence, less than about 20 nm at a 20-30 degree angle of incidence, less than about 15 nm at a 20-30 degree angle of incidence, less than about 10 nm at a 20-30 degree angle of incidence, etc. Similarly, the optical filter 510 is associated with, for example, a variation in center wavelength of less than about 40 nm at an approximately 30-40 degree angle of incidence, less than about 35 nm at an approximately 30-40 degree angle of incidence, less than about 30 nm at an approximately 30-40 degree angle of incidence, less than about 25 nm at an approximately 30-40 degree angle of incidence, less than about 20 nm at an approximately 30-40 degree angle of incidence, etc.

As mentioned above, Figures 5A-5C are provided as examples only. Other examples are possible and may differ from the examples described with respect to Figures 5A-5C.

Thus, germanium hydride optical filters, such as those having germanium hydride as a high refractive index layer and another material as a low refractive index layer, can provide improved angular offset, improved transmittance, and reduced physical thickness relative to other materials used for optical filters associated with a spectral range having a center wavelength of approximately 1550 nm.

The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the embodiments to the precise form disclosed. Modifications and variations are possible in light of the above disclosure or may be acquired from practice of the embodiments.

Some embodiments are described herein in conjunction with threshold values. As used herein, satisfying a threshold value may refer to a value being greater than a threshold value, more than a threshold value, higher than a threshold value, greater than or equal to a threshold value, less than a threshold value, less than a threshold value, lower than a threshold value, less than or equal to a threshold value, equal to a threshold value, etc.

Although particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of possible implementations. In fact, many of these features can be combined in ways not specifically recited in the claims and/or disclosed in the specification. Although each dependent claim listed below may be directly dependent on only one claim, the disclosure of possible implementations includes each dependent claim in combination with every other claim in the claim set.

Unless explicitly stated, any element, action or instruction used herein should not be interpreted as key or necessary. In addition, the articles "a" and "an" used herein are intended to include one or more projects and can be used interchangeably with "one or more". In addition, as used herein, the term "set" is intended to include one or more projects (for example, related projects, unrelated projects, a combination of related projects and unrelated projects, etc.), and can be used interchangeably with "one or more". In the case of only intending to illustrate an project, the term "one" or similar language is used. In addition, the terms "has", "have", "having" etc. used herein are intended to be open terms. In addition, unless explicitly stated otherwise, the term "based on" is intended to represent "at least partially based on".

Claims (18)

1. A bandpass filter, comprising: A set of layers, including: First subset level, The first subset layer is germanium hydride having a first refractive index; and Second subset level, The second subset layer comprises a material having a second refractive index. The second refractive index is less than the first refractive index, and The material includes at least one of the following: Silica material, Alumina materials Titanium dioxide materials, Niobium pentoxide material, tantalum pentoxide material, or Magnesium fluoride materials Specifically, at a wavelength of approximately 1550 nanometers, the first refractive index is greater than 4.2. 2. The bandpass filter of claim 1, wherein the first subset layer is a high-refractive-index layer H, and the second subset layer is a low-refractive-index layer L; and The set of layers is arranged in at least one of the following ways: (HL) _m -order, (HL) _m -H order, (LH) _m order, or L-(H-L)m order, Where m is the number of alternating H and L layers. 3. The bandpass filter of claim 1, wherein the set of layers is configured to allow light of a threshold portion associated with a spectral range between 1100 nm and 2000 nm to pass through. 4. The bandpass filter of claim 1, wherein the set of layers is configured to allow light of a threshold portion associated with a spectral range between 1400 nm and 2000 nm to pass through. 5. The bandpass filter of claim 1, wherein the set of layers is configured to allow light to pass through a threshold portion of a spectral range having a center wavelength of approximately 1550 nanometers. 6. The bandpass filter of claim 1, wherein the first subset layer is associated with an extinction coefficient less than 0.01 in a spectral range centered at approximately 1550 nm. 7. The bandpass filter of claim 1, wherein the second refractive index is less than 3 in the spectral range of 1100 nm to 2000 nm. 8. The bandpass filter of claim 1, wherein the change in the center wavelength of the spectral range is less than 40 nanometers for an incident angle from 0 degrees to 40 degrees. 9. The bandpass filter of claim 1, wherein the variation of the center wavelength of the spectral range is less than 30 nanometers for an incident angle from 0 degrees to 40 degrees. 10. The bandpass filter of claim 1, wherein the variation of the center wavelength of the spectral range is less than 20 nanometers for an incident angle from 0 degrees to 30 degrees. 11. The bandpass filter of claim 1, wherein the variation of the center wavelength of the spectral range is less than 10 nanometers for an incident angle from 0 degrees to 20 degrees. 12. An optical filter, comprising: Base; and A set of alternating high-refractive-index and low-refractive-index layers, disposed on the substrate, are used to filter incident light. The optical filter is configured to allow a first portion of the incident light in a spectral range with a center wavelength of approximately 1550 nanometers to pass through, and to reflect a second portion of the incident light that is not in the spectral range. The high refractive index layer is germanium hydride, and The low-refractive-index layer is silicon dioxide. Furthermore, the refractive index of the high-refractive-index layer is greater than 4.2 at a wavelength of approximately 1550 nanometers. 13. The optical filter of claim 12, wherein the high refractive index layer is deposited using a sputtering process. 14. The optical filter of claim 12, wherein the high refractive index layer is annealed. 15. An optical system comprising: An optical filter, configured to filter an input optical signal and provide a filtered input optical signal. The input optical signal includes light from a first light source and light from a second light source. The optical filter includes a set of dielectric thin film layers. The set of dielectric thin film layers includes: The first subset layer of germanium hydride with the first refractive index, A second subset layer of material having a second refractive index less than the first refractive index. Specifically, at a wavelength of approximately 1550 nanometers, the first refractive index is greater than 4.2. The material includes at least one of the following: Silica material, Alumina materials Titanium dioxide materials, Niobium pentoxide material, tantalum pentoxide material, or Magnesium fluoride materials, and The filtered input optical signal includes light from the second light source with reduced intensity relative to the input optical signal; and An optical sensor configured to receive the filtered input optical signal and provide an output electrical signal. 16. The optical system of claim 15, wherein the optical filter is disposed on the sensor element array of the optical sensor. 17. The optical system of claim 15, wherein the optical filter is separated from the sensor element in free space. 18. The optical system of claim 15, wherein the optical filter has a thickness of approximately 5.6 μm.