Highly Stable Semiconductor Lasers and Sensors for III-V and Silicon Photonic Integrated Circuits

Patent metadata

Field	Value
Publication number	US-2021396665-A1
Application number	US-202117407223-A
Country	US
Kind code	A1
Filing date	Aug 20, 2021
Priority date	Jul 13, 2018
Publication date	Dec 23, 2021
Grant date	—

Abstract

Building blocks are provided for on-chip chemical sensors and other highly-compact photonic integrated circuits combining interband or quantum cascade lasers and detectors with passive waveguides and other components integrated on a III-V or silicon. A MWIR or LWIR laser source is evanescently coupled into a passive extended or resonant-cavity waveguide that provides evanescent coupling to a sample gas (or liquid) for spectroscopic chemical sensing. In the case of an ICL, the uppermost layer of this passive waveguide has a relatively high index of refraction that enables it to form the core of the waveguide, while the ambient air, consisting of the sample gas, functions as the top cladding layer. A fraction of the propagating light beam is absorbed by the sample gas if it contains a chemical species having a fingerprint absorption feature within the spectral linewidth of the laser emission.

First claim

What is claimed is:

1 . A chemical sensor, comprising:
a semiconductor laser with highly stable output intensity and spectral characteristics, the semiconductor laser comprising
a laser cavity having a first end, the first end comprising a first facet coated with a first dielectric spacer and a first highly reflective metal or having a first distributed Bragg reflector (DBR) formed therein, the laser cavity further having a second end opposite the first end, the second end comprising a second facet either coated with a second dielectric spacer and a second highly reflective metal or having a second DBR formed therein, the first and second highly reflective metals or DBRs on the first and second ends preventing light from being passed from the ends of the laser cavity and being fed back into the laser cavity following interactions with external optical elements;
the laser cavity further comprising an active gain waveguide section, a passive sensing waveguide section whose top surface is exposed to an ambient sample gas or liquid, and a detector waveguide section, the active gain waveguide, passive sensing waveguide, and detector waveguide sections of the laser cavity each having a corresponding predetermined length;
wherein a wavelength of the passed light is tuned by variation of the operating temperature, current flowing through the active gain waveguide, or other means; and wherein photocurrent flowing through the detector waveguide section provides information about the spectral characteristics of the absorption by the sample gas or liquid when the wavelength of the passed light is tuned.

2 . The chemical sensor according to claim 1 , wherein the laser is an interband cascade laser (ICL), the active narrow-ridge waveguide being formed from an ICL wafer material that includes:
an n + -GaSb substrate; an n-InAs/AlSb superlattice bottom clad on an upper surface of the substrate; a bottom GaSb separate confinement layer (SCL) on an upper surface of the bottom clad; at least one active gain stage on an upper surface of the bottom GaSb SCL; an n-InAs/AlSb superlattice top clad on an upper surface of the active gain stage; and an n + -InAs or n + -InAsSb top contact layer on an upper surface of the top clad; the active narrow-ridge waveguide further including sidewalls of the narrow ridge etched to a depth below the at least one active stage of the first ICL wafer and further including a dielectric layer deposited on the sidewalls of the ridge and a metallization layer deposited on the upper surface of the ridge to provide a top electrical contact; wherein the n + -InAs or n + -InAsSb top contact layer, the n-InAs/AlSb superlattice top clad layer, and the active gain stages of a second ICL wafer material adjacent to the active waveguide are etched away to form the passive sensing waveguide, with the etch stopping near the top of the bottom GaSb SCL so as to leave an n + -GaSb substrate, an n-InAs/AlSb superlattice bottom clad, and some or all of the bottom GaSb separate confinement layer; wherein the passive sensing waveguide further comprises a ridge formed by etching the sidewalls of the passive waveguide to a depth stopping near the top of the n-InAs/AlSb superlattice bottom clad or near the bottom of the bottom GaSb SCL; wherein the detector waveguide includes a corresponding narrow ridge active waveguide that is similar to or the same as the active gain waveguide in the highly stable laser cavity, the detector waveguide further including a top electrical contact configured to detect a photocurrent due to light propagating in the detector waveguide when it is operated at zero bias, under a reverse bias, or under a forward bias below that required to reach the lasing threshold;

3 . The chemical sensor according to claim 1 ,
wherein the laser is a quantum cascade laser (QCL) whose active narrow-ridge waveguide is processed from a QCL wafer. wherein the detector is a quantum cascade detector whose active narrow-ridge waveguide is processed from the QCL wafer.

4 . The chemical sensor according to claim 3 , wherein the passive sensing waveguide is formed using the same processing, ridge width, and etch depth(s) that are used to form the active narrow-ridge waveguide of the laser, but without any dielectric coating of the ridge sidewalls or metal deposited on top.

5 . The chemical sensor according to claim 4 , wherein the passive waveguide is ion bombarded to reduce optical loss in the passive waveguide.

Assignees

• Us Gov Sec Navy

Inventors

• Meyer Jerry R
• Vurgaftman Igor
• Canedy Chadwick Lawrence
• Bewley William W
• Kim Chul Soo
• Merritt Charles D
• Warren Michael V
• Weiblen R Joseph
• Kim Mijin

Classifications

• H01S5/34306

  emitting light at a wavelength longer than 1000nm, e.g. InP based 1300 and 1500nm lasers · CPC title

• H01S5/4087

  emitting more than one wavelength · CPC title

• H01S5/0287

  Facet reflectivity · CPC title

• H01S5/0028

  Laser diodes used as detectors · CPC title

• H01S5/125

  Distributed Bragg reflector [DBR] lasers · CPC title