Bandpass transmission filter and narrowband radiation source

Patent metadata

Field	Value
Publication number	US-11320586-B2
Application number	US-202016810442-A
Country	US
Kind code	B2
Filing date	Mar 5, 2020
Priority date	Mar 8, 2019
Publication date	May 3, 2022
Grant date	May 3, 2022

Abstract

In accordance with an embodiment, a bandpass transmission filter having a center wavelength of transmission includes: a waveguide structure comprising a grating structure having changing grating pitch values configured to diffract radiation in the waveguide structure having a first wavelength lower than the center wavelength of transmission, and configured to reflect radiation in the waveguide structure having a second wavelength higher than the center wavelength of transmission; and a radiation absorbing structure configured to absorb radiation guided by the waveguide structure having a third wavelength higher than the second wavelength, wherein the radiation absorbing structure is an integrated part of the waveguide structure or comprises a layer arranged adjacent to the waveguide structure.

First claim

What is claimed is:

1. A bandpass transmission filter having a center wavelength of transmission, the bandpass transmission filter comprising:
a waveguide structure arranged on a substrate, the waveguide structure comprising a grating structure comprising a side face grating or a front face grating, and comprising changing grating pitch values configured to diffract out radiation in the waveguide structure having first wavelengths lower than a center wavelength of transmission, and configured to reflect back guided radiation in the waveguide structure having a second wavelength higher than the center wavelength of transmission; and
a radiation absorbing structure configured to absorb radiation guided by the waveguide structure having a third wavelength higher than the second wavelength, wherein:
the radiation absorbing structure comprises a first dielectric layer arranged adjacent to the waveguide structure,
the radiation absorbing structure at least partially covers at least one of a side face, a bottom face and a top face of the waveguide structure with the grating structure,
a second dielectric layer is formed between the waveguide structure and the substrate,
the waveguide structure comprises a polysilicon (Poly-Si), Si, Ge, Si 3 N 4 , AIN, or As 2 Se 3 material,

the first dielectric layer comprises a Si 3 N 4 material, and
the second dielectric layer comprises a SiO 2 material.

2. The bandpass transmission filter according to claim 1 , wherein the changing grating pitch values depend on at least one of a linear function, an exponential function or a polynomial function.

3. The bandpass transmission filter according to claim 1 , wherein the changing grating pitch values comprise a combination of a basis pitch value and a variable pitch value, wherein the variable pitch value changes linearly, exponentially or polynomially.

4. The bandpass transmission filter according to claim 1 , wherein the grating structure comprises a chirped grating structure having monotonically changing grating pitch values.

5. The bandpass transmission filter according to claim 1 , wherein:
the first dielectric layer is arranged between the waveguide structure and the substrate, and the second dielectric layer is arranged between the first dielectric layer and the substrate.

6. The bandpass transmission filter according to claim 5 , wherein the second dielectric layer has a material thickness for suppressing a coupling of a waveguide mode from the waveguide structure into the substrate.

7. The bandpass transmission filter according to claim 1 , wherein the waveguide structure comprises a strip waveguide having the side face grating or the top face grating.

8. The bandpass transmission filter according to claim 1 , wherein the waveguide structure comprises a slot waveguide having the side face grating or the top face grating.

9. The bandpass transmission filter according to claim 1 , wherein the waveguide structure is a slab waveguide having the top face grating.

10. The bandpass transmission filter according to claim 1 , wherein the waveguide structure comprises a waveguide extension structure without having arranged thereon a chirped grating structure, wherein the radiation absorbing structure at least partially covers a face of the waveguide extension structure for reducing a sideband transmission of the bandpass transmission filter.

11. The bandpass transmission filter according to claim 1 , wherein the changing grating pitch values Λ_i depend on a combination of a basis pitch value and a variable pitch value, and wherein the variable pitch value changes according to:
a linear function with Λ_i=Λ_o+ΔΛ×i, wherein “Λ_o” is the basis pitch value and “ΔΛ×i” is the variable pitch value, or
a linear function with Λ_i=Λ_o+ΔΛ×(N−i), wherein “Λ_o” is the basis pitch value and “ΔΛ×(N−i)” is the variable pitch value, or
an exponential function with Λ_i=Λo+ (F_1) {circumflex over ( )}i, wherein “Λ_o” is the basis pitch value and (F_1) {circumflex over ( )}i is the variable pitch value, or
an exponential function with Λ_i=Λ_o× (F_2) {circumflex over ( )}i, wherein “Λ_o” is the basis pitch value and (F_2) {circumflex over ( )}iis the variable pitch value, or
an polynomial function with Λ_i=Λ_o+Σ_(k=1){circumflex over ( )}n Λ_k i{circumflex over ( )}k , wherein “Λ_o” is the basis pitch value and “Σ_(k=1){circumflex over ( )}n Λ_k i{circumflex over ( )}k ” is the variable pitch value.

12. The bandpass transmission filter according to claim 11 , wherein the basis pitch value “Λ_o” comprises a center pitch value “Λ_Center” and an additional gap value “Λ_Gap”, and wherein the term “Λ_Center” depends on the function:
Λ_Center=λ m/ 2 n _ eff,

wherein λ m is the center wavelength of transmission, n eff is an effective mode index of a mode that propagates in the waveguide structure, and m is the diffraction order, and wherein the additional gap value “Λ_Gap” is provided to avoid Bragg reflections of the guided radiation at the center wavelength.

13. The bandpass transmission filter according to claim 1 , wherein an i-th grating pitch value Λ_i of the grating pitch values is repeated N-times where N is an integer greater or equal to 4.

14. A narrowband radiation source comprising:
the bandpass transmission filter of claim 1 , further comprising a broadband radiation source,
wherein the bandpass transmission filter is arranged in a radiation emission direction of the broadband radiation source downstream to the broadband radiation source.

15. The narrowband radiation source according to claim 14 , wherein the radiation absorbing structure is integrated with the waveguide structure.

16. A method, comprising:
generating broadband radiation using a thermal emitter; and
filtering the broadband radiation to produce narrowband radiation using the bandpass transmission filter of claim 1 .

Assignees

• Infineon Technologies Ag

Inventors

• Tortschanoff Andreas
• Consani Cristina
• Grille Thomas
• Jakoby Bernhard
• Ranacher Christian

Classifications

• G02B5/208

  for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation · CPC title

• G02B6/02085

  characterised by the grating profile, e.g. chirped, apodised, tilted, helical · CPC title

• G02B2006/12107

  Grating · CPC title

• G02B2006/12097

  Ridge, rib or the like · CPC title

• G02B2006/12061

  Silicon · CPC title