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US-20260128567-A1 - TUNABLE LASERS AND THEIR SENSING APPLICATIONS

US20260128567A1US 20260128567 A1US20260128567 A1US 20260128567A1US-20260128567-A1

Abstract

The process of heating up a cavity with a diode laser or light beam source with a booster current pulse followed by application of a drive to the diode to produce a continuous wave (CW) over time while the cavity cools (spontaneously or otherwise), or by the application of pulses of current to produce pulsed waves of different wavelengths allows for fast tuning of wavelength laser or light emissions. These processes may be used with sensing fibers to sense a variety of different parameters including but not limited to temperature, strain, gas concentration, etc.

Inventors

  • Dyson BUITENKAMP
  • Logan THEIS

Assignees

  • SENTEK INSTRUMENT, LLC

Dates

Publication Date
20260507
Application Date
20231006

Claims (17)

  1. 1 . A method for tuning a laser or light source, comprising: initially heating a cavity of a diode laser or light source by providing a booster current pulse to the cavity; and then during temperature decay after the booster current pulse, i) driving the diode laser or light source with successive current pulses to produce laser beams or light beams of different wavelengths based on differences in a temperature of the cavity, or ii) driving the diode laser or light source with a continuous current for a selected time period to produce laser beams or light beams of different wavelengths based on differences in a temperature of the cavity over the time period.
  2. 2 . The method of claim 1 wherein i) is performed and wherein a wavelength change from pulse to pulse of the laser beams or light beams is uniform.
  3. 3 . The method of claim 1 wherein i) is performed and wherein a wavelength change from pulse to pulse of the laser beams or light beams is non-uniform.
  4. 4 . The method of claim 1 wherein the diode laser or light source is a diode laser selected from the group consisting of a distributed feedback laser, a distributed Bragg reflector, a Fabry-Perot laser, a vertical cavity surface emitting laser, a quantum well laser, a multi quantum well laser, and a quantum dot laser.
  5. 5 . The method of claim 1 wherein the diode laser or light source is a diode light source selected from the group consisting of a light emitting diode and a superluminescent diode.
  6. 6 . The method of claim 1 wherein ii) is performed.
  7. 7 . A method for providing a tuned pulsed laser or light beam, comprising: producing a continuous wave laser or light beam using a driving current; and chopping the continuous wave laser or light beam into temporal pulses using an optical modulator that is positioned to receive the continuous wave laser or light beam, wherein the temporal pulses have different wavelengths.
  8. 8 . The method of claim 7 wherein the driving current is varied with time during chopping.
  9. 9 . The method of claim 7 wherein the driving current is not varied with time during chopping.
  10. 10 . The method of claim 7 wherein, during the producing step, the driving current is modulated at a speed where a charge carrier density effect is dominant.
  11. 11 . A device for providing a tuned pulsed laser beam, comprising: a continuous wave laser beam source; a source of laser driving current connected to the continuous wave laser beam source; and an optical modulator positioned to chop a continuous wave laser produced by the continuous wave laser beam source into temporal pulses having different wavelengths.
  12. 12 . The device of claim 11 wherein the optical modulator is integral with the continuous wave laser beam source.
  13. 13 . The device of claim 11 wherein the optical modulator is an electroabsorption modulator.
  14. 14 . A sensor, comprising a source of a tuned pulsed laser or light beam; a sensing fiber positioned to receive a pulsed laser or light beam from said source of the tuned pulsed laser or light beam; and a detector for detecting the pulsed laser or light beam after passing through at least a portion of the sensing fiber, wherein the source of the tuned pulsed laser or light beam comprises i) a cavity a diode laser or light source positioned in the cavity, wherein the cavity is heatable by applying a booster current pulse to the cavity, followed by a temperature decay, and wherein the diode laser or light source is drivable by with successive current pulses to produce laser beams or light beams of different wavelengths based on differences in a temperature of the cavity, or wherein the diode laser or light source is drivable with a continuous current for a selected time period to produce laser beams or light beams of different wavelengths based on differences in a temperature of the cavity over the time period, or ii) a continuous wave laser beam source, a source of laser driving current connected to the continuous wave laser beam source, and an optical modulator positioned to chop a continuous wave laser produced by the continuous wave laser beam source into temporal pulses having different wavelengths.
  15. 15 . The sensor of claim 14 wherein the sensing fiber has one or more Bragg gratings or Fabry Perot interferometers positioned in or connected to the sensing fiber.
  16. 16 . The sensor of claim 15 wherein the sensing fiber has a plurality of spaced apart Bragg gratings or Fabry Perot interferometers positioned in or connected to the sensing fiber, wherein different Bragg gratings or different Fabry Perot interferometers in the plurality are responsive to different wavelengths of the pulsed laser or light beam.
  17. 17 . The sensor of claim 14 wherein a reflectivity of the Bragg gratings or Fabry Perot interferometers changes depending on strain or temperature operating on the sensing fiber.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Ser. No. 63/414,084 filed Oct. 7, 2022, and to U.S. Ser. No. 63/535,275 filed Aug. 29, 2023, and the complete contents of both is herein incorporated by reference. BACKGROUND Diode lasers have found a wide range of applications such as communication, sensing, metrology and light detection and ranging (LIDAR). Many of these applications may require the wavelength of laser emission to change in time. One of the most common methods for wavelength tuning is to change the laser chip temperature by the control of the electric current injected into a thermo-electric cooler (TEC) to which the laser chip is mounted or attached. Given the relatively large thermal mass of the TEC, the wavelength tuning is usually in the order of multiple seconds for a few nanometer wavelength change. Sakano et al. (U.S. Pat. No. 5,173,909) patented a method for improved thermal tuning speed by a special diode laser structure in which a temperature variable heater separated from an active layer (lasing region) by a distance less than the thickness of a compound semiconductor substrate. Because the heater is located very close to the active layer, the response time of temperature change is improved. This method requires a new laser diode structure. In addition to the laser driving circuit, a separate circuit for the laser heating is also necessary. All these will increase the laser cost. Njegovee et al. (US 2014/0112361 A1) describes a method for fast diode laser tuning. In their method, a diode laser is driven by a very narrow pulse (well below 1 ms) that has a peak current in the order of multiple amperes. During the transitions of the current including the up and down slopes of the current pulse, the optical power varies but the laser wavelength changes at the same time. The varying optical power with the tuned wavelength is utilized for various purposes such as demodulation of Fabry-Perot interferometers. Besides the methods above, another common method of wavelength tuning is the use of an external cavity. This method can offer a large wavelength tuning range sometimes at high speed. However, these types of lasers are often very expensive, typically thousands of dollars or more. Optical fiber tunable lasers are also available which could provide fast and wide wavelength tuning. However, unlike diode lasers where laser pulses can easily be generated by direct current modulation, fiber lasers are often not as easy in controlled pulse generation. In addition, similar to external cavity diode tunable lasers, these tunable fiber lasers are expensive and often susceptible to ambient vibration. SUMMARY Aspects of the invention pertain to methods and apparatuses for the generation of fast wavelength tuning laser emissions which may be pulses or continuous wave (CW). The laser diode may be but is not limited to a distributed feedback (DFB) laser, a distributed Bragg reflector (DBR) laser, a Fabry-Perot (FP) laser, a vertical-cavity surface emitting laser (VCSEL), a quantum well or multi-quantum well laser, a quantum dot laser or any other laser whose emission wavelength can be tuned by laser chip temperature control. In one embodiment, a DFB laser is used as an example to explain the operation of a wavelength-tunable pulsed laser generation. Also, aspects of the invention may also be applied to other diodes that emit light. Example diodes may include but are limited to light emitting diodes (LEDs) and superluminescent diodes (SLDs). DESCRIPTION OF THE DRAWINGS FIG. 1a is a graph showing an initial booster pulse followed by a plurality of wavelength tunable pulses. FIG. 1b is a graph showing an initial increase in laser temperature followed by a spontaneous cool down. FIG. 2 is a schematic diagram of a device wherein the cavity can be heated up quickly using a booster pulse as shown in FIG. 1a. FIG. 3 is a schematic diagram of a second embodiment of the invention where an optical modulator is used to chop a continuous wave laser into temporal pulses. FIG. 4 is a graph showing the laser driving current and different wavelength pulses produced by an EAM voltage control. FIG. 5 is a schematic showing a wavelength tunable laser being used in a sensing application with an optical fiber. FIG. 6a is a graph showing an initial booster pulse followed by current for producing a continuous wave laser or light beam where the wavelength changes over time. FIG. 6b is a graph for the device and methodology described in FIG. 6a showing an initial increase in laser temperature followed by a spontaneous cool down. FIG. 7 is a schematic showing a different wavelength tunable laser being used in a sensing application with an optical fiber. FIG. 8a-b are schematics showing a sensor for gas concentration measurements, and FIG. 8c is a graph representing a response for a gas concentration measurement. FIG. 9 is a schematic of an exemplary optical frequency-domain reflector system base