Apparatus, systems, and methods for on-chip spectroscopy using optical switches

Patent metadata

Field	Value
Publication number	US-10852190-B2
Application number	US-201916506142-A
Country	US
Kind code	B2
Filing date	Jul 9, 2019
Priority date	Feb 10, 2016
Publication date	Dec 1, 2020
Grant date	Dec 1, 2020

Abstract

A spectrometer includes an interferometer having a first interference arm and a second interference arm to produce interference patterns from incident light. At least one of the interference arms includes a series of cascaded optical switches connected by two (or more) waveguides of different lengths. Each optical switch directs the incident light into one waveguide or another, thereby changing the optical path length difference between the first interference arm and the second interference arm. This approach can be extended to multi-mode incident light by placing parallel interferometers together, each of which performs spectroscopy of one single mode in the multi-mode incident light. To maintain the compactness of the spectrometer, adjacent interferometers can share one interference arm.

First claim

The invention claimed is:

1. A spectrometer, comprising:
a beam splitter to split incident light into a first portion and a second portion;
a first interference arm, in optical communication with the beam splitter, to receive the first portion of the incident light, the first interference arm comprising:
first optical switches, each first optical switch switchable between a first state and a second state;
first variable waveguides and first reference waveguides, wherein each first optical switch is coupled to a corresponding first variable waveguide and a corresponding first reference waveguide, each first variable waveguide to receive the first portion of the incident light when its corresponding first optical switch is in its first state, each first reference waveguide to receive the first portion of the incident light when its corresponding first optical switch is in its second state, wherein an optical path length of each first variable waveguide is longer than an optical path length of its corresponding first reference waveguide;

a second interference arm, in optical communication with the beam splitter, to receive the second portion of the incident light, the second interference arm comprising:
second optical switches, each second optical switch switchable between a first state and a second state;
second variable waveguides and second reference waveguides, wherein each second optical switch is coupled to a corresponding second variable waveguide and a corresponding second reference waveguide, each second variable waveguide to receive the second portion of the incident light when its corresponding second optical switch is in its first state, each second reference waveguide to receive the second portion of the incident light when its corresponding second optical switch is in its second state, wherein an optical path length of each second variable waveguide is shorter than an optical path length of its corresponding second reference waveguide; and

a detector, in optical communication with the first interference arm and the second interference arm, to detect interference of the first portion of the incident light from the first interference arm and the second portion of the incident light from the second interference arm.

2. The spectrometer of claim 1 , wherein each first optical switch and each second optical switch is a Mach-Zehnder interferometer (MZI).

3. The spectrometer of claim 1 , wherein each first optical switch and each second optical switch includes:
a first switch arm;
a second switch arm;
a first electrode, in electrical communication with the first switch arm, and a second electrode, in electrical communication with the first switch arm and the second switch arm, to modulate a refractive index of the first switch arm; and
a third electrode, in electrical communication with the second switch arm, to modulate a refractive index of the second switch arm with the second electrode.

4. The spectrometer of claim 3 , wherein each first optical switch further includes:
a first multi-mode interferometer (MMI) including a first input port to receive the first portion of the incident light and a pair of first output ports to output the first portion of the incident light via the pair of first output ports; and
a second MMI including a pair of second input ports to receive the first portion of the incident light from the first MMI and a second output port to output the first portion of the incident light,
wherein the first switch arm optically couples one of the first output ports to one of the second input ports, and wherein the second switch arm optically couples the other of the first output ports to the other of the second input ports.

5. The spectrometer of claim 3 , wherein each second optical switch further includes:
a first multi-mode interferometer (MIMI) including a first input port to receive the second portion of the incident light and a pair of first output ports to output the second portion of the incident light via the pair of first output ports; and
a second MMI including a pair of second input ports to receive the second portion of the incident light from the first MMI and a second output port to output the second portion of the incident light,
wherein the first switch arm optically couples one of the first output ports to one of the second input ports, and wherein the second switch arm optically couples the other of the first output ports to the other of the second input ports.

6. The spectrometer of claim 1 , further comprising a beam combiner coupled to the first interference arm, the second interference arm, and the detector, to transmit the first portion of the incident light from the first interference arm and the second portion of the incident light from the second interference arm to the detector.

7. A method of spectroscopy, the method comprising:
splitting incident light into a first portion and a second portion;
coupling the first portion of the incident light into a first interference arm, the first interference arm including:
first optical switches;
first variable waveguides and first reference waveguides, wherein an optical path length of each first variable waveguide is longer than an optical path length of its corresponding first reference waveguide,
the coupling including coupling the first portion of the incident light into each first variable waveguide when its corresponding first optical switch is in a first state,
the coupling further including coupling the first portion of the incident light into each first reference waveguide when its corresponding first optical switch is in a second state;

coupling the second portion of the incident light into a second interference arm, the second interference arm including:
second optical switches;
second variable waveguides and second reference waveguides, wherein an optical path length of each second variable waveguide is shorter than an optical path length of its corresponding second reference waveguide,
the coupling including coupling the second portion of the incident light into each second variable waveguide when its corresponding second optical switch is in a first state,
the coupling further including coupling the second portion of the incident light into each second reference waveguide when its corresponding second optical switch is in a second state;

actuating the first optical switches to couple the first portion of the incident light through at least one of the first variable waveguides, or at least one of the first reference waveguides, or combinations thereof;
actuating the second optical switches to couple the second portion of the incident light through at least one of the second variable waveguides, or at least one of the second reference waveguides, or combinations thereof; and
detecting interference between the first portion of the incident light from the first interference arm and the second portion of the incident light from the second interference arm.

8. The method of claim 7 , wherein each first optical switch and each second optical switch is a Mach-Zehnder interferometer (MZI).

9. A spectrometer, comprising:
a beam splitter to split incident light into a first portion and a second portion;
a first interference arm, in optical communication with the beam splitter, to receive the first portion of the incident light, the first interference arm comprising:
first optical switches, each first optical switch switchable between a first state and a second state;
first variable waveguides and first reference waveguides, wherein each first optical switch is coupled to a corresponding first variable waveguide and a corresponding first reference waveguide, each first variable waveguide to receive the f

Assignees

• Massachusetts Inst Technology

Inventors

• Hu Juejun
• Gu Tian
• Lin Hongtao
• Kita Derek
• Agarwal Anuradha M

Classifications

• G02F1/311

  Cascade arrangement of plural switches · CPC title

• G01J3/4531 Primary

  Devices without moving parts · CPC title

• G02F1/313

  in an optical waveguide structure · CPC title

• G01J3/0218

  using optical fibers · CPC title

• G02F1/3136

  of interferometric switch type · CPC title