Thin-film filter for tunable laser

Patent metadata

Field	Value
Publication number	US-11575245-B2
Application number	US-202016805526-A
Country	US
Kind code	B2
Filing date	Feb 28, 2020
Priority date	Feb 28, 2020
Publication date	Feb 7, 2023
Grant date	Feb 7, 2023

Abstract

A thin-film device for a wavelength-tunable semiconductor laser. The device includes a cavity between a high-reflectivity facet and an anti-reflection facet designed to emit a laser light of a wavelength in a tunable range determined by two Vernier-ring resonators with a joint-free-spectral-range between a first wavelength and a second wavelength. The device further includes a film including multiple pairs of a first layer and a second layer sequentially stacking to an outer side of the high-reflectivity facet. Each layer in each pair has one unit of respective optical thickness except one first or second layer in one pair having a larger optical thickness. The film is configured to produce inner reflectivity of the laser light from the high-reflectivity facet at least >90% for wavelengths in the tunable range starting from the first wavelength but at least <50% for wavelengths in a 25 nm range around the second wavelength.

First claim

What is claimed is:

1. A wavelength tunable semiconductor laser comprising:
a wavelength tunable optical filter formed in a silicon photonics substrate and configured to yield a joint free-spectral-range between a first wavelength and a second wavelength;
a phase matcher comprising a waveguide formed in the silicon photonics substrate and coupled to the wavelength tunable optical filter;
a gain chip comprising a lasing cavity having an active region disposed between a high-reflectivity facet and an anti-reflection facet having an exit port coupled to the waveguide of the phase matcher, the lasing cavity being configured to generate a laser light in the active region and to emit the laser light out the exit port; and
a thin film filter disposed on an outer side of the high-reflectivity facet, the thin film filter formed of a stack of multiple pairs of filter layers, the multiple pairs of filter layers comprising a plurality of first filter layers comprising a first material alternating with a plurality of second filter layers comprising a second material, each of the multiple pairs of filter layers containing one of the first filter layers overlying one of the second filter layers, the first filter layers having a first thickness and a first optical thickness, each of the plurality of second filter layers having a second thickness different from the first thickness and a second optical thickness equal to the first optical thickness, and at least one of the first filter layers in one of the multiple pairs having a third thickness greater than the first thickness and a third optical thickness that is greater than the first optical thickness.

2. The wavelength tunable semiconductor laser of claim 1 wherein the first filter layer in each pair of filter layers is more distal to the outer side of the high-reflectivity facet than the second filter layer in the same pair of filter layers.

3. The wavelength tunable semiconductor laser of claim 1 wherein each first filter layer of the alternating pairs of filter layers comprises a high-refractive index material and each second layer of the alternating pairs of filter layers comprises a low-refractive index material having a refractive index that is lower than the high-refractive index material.

4. The wavelength tunable semiconductor laser of claim 1 wherein the wavelength tunable optical filter comprises at least two ring resonators formed as respective ring-shaped waveguides in the silicon photonics substrate, each ring-shaped waveguide having different radius.

5. The wavelength tunable semiconductor laser of claim 4 wherein the wavelength tunable optical filter further comprises resistive thin-film heaters overlying respective ones of at least two ring resonators to provide wavelength tuning of the laser light up to a tunable range in an extended C-band from the first wavelength at 1526 nm to a mid-point of the joint-free-spectral-range at 1568 nm.

6. A wavelength tunable semiconductor laser, comprising:
a wavelength tunable optical filter formed in a silicon photonics substrate and configured to yield a joint free-spectral-range between a first wavelength and a second wavelength;
a phase matcher comprising a waveguide formed in the silicon photonics substrate and coupled to the wavelength tunable optical filter;
a gain chip comprising a lasing cavity having an active region disposed between a high-reflectivity facet and an anti-reflection facet having an exit port coupled to the waveguide of the phase matcher, the lasing cavity being configured to generate a laser light in the active region and to emit the laser light out the exit port;
a thin film filter disposed on an outer side of the high-reflectivity facet, the thin film filter formed of a stack of alternating pairs of filter layers, each respective pair of filter layers containing a first filter layer overlying a second filter layer, among which a plurality of first filter layers have a first optical thickness, a plurality of second filter layers having a second optical thickness equal to the first optical thickness, and at least one first filter layer having a third optical thickness that is greater than the first optical thickness; and
a wavelength locker coupled to the wavelength tunable optical filter and a semiconductor optical amplifier having a second gain chip configured to amplify the laser light with a single wavelength tuned by the wavelength tunable optical filter and locked by the wavelength locker before outputting the laser light with the single wavelength substantially free from the second wavelength.

7. A wavelength tunable semiconductor laser, comprising:
a wavelength tunable optical filter formed in a silicon photonics substrate and configured to yield a joint free-spectral-range between a first wavelength and a second wavelength;
a phase matcher comprising a waveguide formed in the silicon photonics substrate and coupled to the wavelength tunable optical filter;
a gain chip comprising a lasing cavity having an active region disposed between a high-reflectivity facet and an anti-reflection facet having an exit port coupled to the waveguide of the phase matcher, the lasing cavity being configured to generate a laser light in the active region and to emit the laser light out the exit port; and
a thin film filter disposed on an outer side of the high-reflectivity facet, the thin film filter formed of a stack of alternating pairs of filter layers, each respective pair of filter layers containing a first filter layer overlying a second filter layer, among which a plurality of first filter layers have a first optical thickness, a plurality of second filter layers having a second optical thickness equal to the first optical thickness, and at least one first filter layer having a third optical thickness that is greater than the first optical thickness,
wherein the thin film filter is configured to provide at least 90% inner reflectivity for the laser light from the high-reflectivity facet at any wavelength within a spectral range between the first wavelength to a mid-point of a joint-free-spectral-range and less than 50% inner reflectivity for any wavelength within a 25 nm band surrounding the second wavelength.

8. A wavelength tunable semiconductor laser, comprising:
a wavelength tunable optical filter formed in a silicon photonics substrate and configured to yield a joint free-spectral-range between a first wavelength and a second wavelength;
a phase matcher comprising a waveguide formed in the silicon photonics substrate and coupled to the wavelength tunable optical filter;
a gain chip comprising a lasing cavity having an active region disposed between a high-reflectivity facet and an anti-reflection facet having an exit port coupled to the waveguide of the phase matcher, the lasing cavity being configured to generate a laser light in the active region and to emit the laser light out the exit port; and
a thin film filter disposed on an outer side of the high-reflectivity facet, the thin film filter formed of a stack of alternating pairs of filter layers, each respective pair of filter layers containing a first filter layer overlying a second filter layer, among which a plurality of first filter layers have a first optical thickness, a plurality of second filter layers having a second optical thickness equal to the first optical thickness, and at least one first filter layer having a third optical thickness that is greater than the first optical thickness,
wherein the active region of the gain chip is configured as a linear waveguide and comprises an indium phosphide PN junction disposed in the linear waveguide.

9. A wavelength tunable semiconductor laser, comprising:
a wavelength tunable optical filter formed in a

Assignees

• Marvell Asia Pte Ltd

Inventors

• He Xiaoguang
• Nagarajan Radhakrishnan L
• Taylor Brian

Classifications

• H01S5/32391

  based on In(Ga)(As)P · CPC title

• H04B10/503

  Laser transmitters · CPC title

• G02F1/011 Primary

  in optical waveguides, not otherwise provided for in this subclass · CPC title

• H01S5/101

  Curved waveguide (H01S5/1243 takes precedence) · CPC title

• H01S3/106

  by controlling devices placed within the cavity ({H01S3/10076,} H01S3/13 take precedence) · CPC title