Wavelength locker using multiple feedback curves to wavelength lock a beam

Patent metadata

Field	Value
Publication number	US-10050405-B2
Application number	US-201615132797-A
Country	US
Kind code	B2
Filing date	Apr 19, 2016
Priority date	Apr 19, 2016
Publication date	Aug 14, 2018
Grant date	Aug 14, 2018

Abstract

A device may include a first photodetector to generate a first current based on an optical power of an optical beam. The device may include a beam splitter to split a portion of the optical beam into a first beam and a second beam. The device may include a wavelength filter to filter the first beam and the second beam. The wavelength filter may filter the second beam differently than the first beam based on a difference between an optical path length of the first beam and an optical path length of the second beam through the wavelength filter. The device may include second and third photodetectors to respectively receive, after the wavelength filter, the first beam and the second beam and to generate respective second currents.

First claim

What is claimed is:

1. A device, comprising:
a laser emitter to generate a laser beam to be wavelength locked to a target frequency based on an emission frequency to be measured by the device;
a first photodetector to generate a first current based on a first optical power of the laser beam,
the laser beam to be wavelength locked based on the first current;

a beam splitter to split a portion of the laser beam into a first beam, a second beam, a third beam, and a fourth beam;
an etalon to filter the first beam and the second beam based on the emission frequency of the laser beam,
the etalon to have different optical path lengths for the first beam and the second beam,
the different optical path lengths for the first beam and the second beam being configured to cause a frequency offset between a first curve corresponding to the first beam and a second curve corresponding to the second beam,
the etalon to filter the first beam and the second beam to a second optical power and a third optical power, respectively, based on the different optical path lengths in the etalon, and
the third beam being received by the first photodetector without being filtered by the etalon; and

second and third photodetectors to generate respective second currents,
a selected current, of the respective second currents, to be used to wavelength lock the laser beam,
the selected current to be selected based on which of the respective second currents will provide a more accurate measurement of the emission frequency, and

the second and third photodetectors to generate the respective second currents based on the second optical power and the third optical power, respectively.

2. The device of claim 1 , where
the first curve describes a relationship between the second optical power, an optical path length, of the different optical path lengths, of the first beam, and the emission frequency,
the second curve describes a relationship between the third optical power, an optical path length, of the different optical path lengths, of the second beam, and the emission frequency, and
a controller of the device is configured to select the selected current based on a location on the first curve and the second curve of a point corresponding to the target frequency.

3. The device of claim 2 , where the controller is configured to select a second current, of the respective second currents, corresponding to the first beam when a slope of the first curve is steeper than a slope of the second curve at the point, and
where the controller is configured to select a second current, of the respective second currents, corresponding to the second beam when the slope of the second curve is steeper than the slope of the first curve at the point; and
where the controller is configured to determine the emission frequency based on a ratio of the selected second current to a reference current and based on a curve, of the first curve and the second curve, that corresponds to the selected current.

4. The device of claim 3 , where the controller is configured to generate a feedback signal to cause the laser emitter to modify the emission frequency based on a difference between the emission frequency and the target frequency.

5. The device of claim 1 , where the etalon further comprises a coating or a patterned surface to cause an optical path length, of the respective optical path lengths, of the first beam to be different than an optical path length, of the respective optical path lengths, of the second beam.

6. The device of claim 5 , where the beam splitter comprises a walkoff splitter to cause a particular spatial separation between the first beam and the second beam,
the particular spatial separation to cause one of the first beam or the second beam to be transmitted through the coating or the patterned surface.

7. The device of claim 1 , where the beam splitter comprises a wedge splitter to cause an angular separation between the first beam and the second beam to cause an optical path length, of the respective optical path lengths, of the first beam to be different than an optical path length, of the respective optical path lengths, of the second beam.

8. The device of claim 1 , where the beam splitter comprises:
a first reflective surface to partially reflect the laser beam to form the first beam, and to partially pass the laser beam to a second reflective surface,
the second reflective surface to partially pass the laser beam to the first photodetector, and partially reflecting the laser beam to form the second beam.

9. The device of claim 1 , where the portion of the laser beam comprises the first beam and the second beam; and
where the beam splitter receives the portion of the laser beam from the etalon; and
where the etalon further comprises:
a component that is configured to have a first refractive index for the first beam and a second refractive index for the second beam,
the first refractive index being different than the second refractive index.

10. A device, comprising:
a first photodetector to generate a first current based on an optical power of an optical beam;
a beam splitter to split a portion of the optical beam into a first beam, a second beam, a third beam, and a fourth beam;
a wavelength filter to filter the first beam and the second beam,
the wavelength filter to filter the second beam differently than the first beam based on a difference between an optical path length of the first beam and an optical path length of the second beam through the wavelength filter,
the optical path length of the first beam and the optical path length of the second beam being configured to cause a frequency offset between a first curve corresponding to the first beam and a second curve corresponding to the second beam, and
the third beam being received by the first photodetector without being filtered by the wavelength filter; and

second and third photodetectors to respectively receive, after the wavelength filter, the first beam and the second beam and to generate respective second currents.

11. The device of claim 10 , further comprising:
a controller to generate a feedback signal based on the first current and a selected one of the respective second currents.

12. The device of claim 11 , where the controller is configured to:
select the selected one of the respective second currents based on a target frequency for the optical beam.

13. The device of claim 11 , further comprising:
an emitter to generate the optical beam; and
where the controller is configured to drive the emitter based on the feedback signal.

14. The device of claim 10 , where the difference between the optical path length of the first beam and the optical path length of the second beam through the wavelength filter is associated with a difference in at least one of:
a thickness of the wavelength filter for an optical path of the first beam compared to an optical path of the second beam;
an incident angle to the wavelength filter for the optical path of the first beam compared to the optical path of the second beam; or
a difference in a material property of a portion of the wavelength filter for the optical path of the first beam compared to the optical path of the second beam.

15. The device of claim 10 , where the difference between the optical path length of the first beam and the optical path length of the second beam through the wavelength filter is associated with a frequency shift in a feedback curve for the optical path length of the first beam compared to a feedback curve for the optical path length of the second beam.

Assignees

• Lumentum Operations Llc

Inventors

• Xiong Wei
• Larson Michael C
• Colbourne Paul
• Mclaughlin Sheldon

Classifications

• H01S3/005

  Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping (shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B) · CPC title

• G02B6/4286

  Optical modules with optical power monitoring · CPC title

• H01S5/005

  Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping (H01S5/026, H01S5/18388 take precedence) · CPC title

• G02B6/4296

  coupling with sources of high radiant energy, e.g. high power lasers, high temperature light sources · CPC title

• H01S3/10061

  Polarization control · CPC title