CN112789773A

CN112789773A - Laser module with multiple component lasers

Info

Publication number: CN112789773A
Application number: CN201980063831.4A
Authority: CN
Inventors: G·帕特里奇; R·P·泰拉
Original assignee: Agilent Technologies Inc
Current assignee: Agilent Technologies Inc
Priority date: 2018-09-30
Filing date: 2019-07-25
Publication date: 2021-05-11
Also published as: JP7398437B2; DE112019004915T5; WO2020068260A1; JP2022501806A

Abstract

A laser module having a plurality of component lasers is disclosed. Each component laser is characterized by a gain chip, a diffraction grating structure, a pivot point, and an output laser beam that travels in an output beam direction. A drive shaft is coupled to each pivot point and rotates each diffraction grating structure about the pivot point associated with the constituent laser. The module further includes a plurality of reflectors, each positioned to receive an output laser beam from one of the plurality of component lasers and direct the output laser beam along an output path common to all of the component lasers. The controller controls the rotation angle of the drive shaft.

Description

Laser module with multiple component lasers

Background

Many of the measurements of interest involve measuring the response of the sample to a light beam of known wavelength as a function of wavelength. Many of the measured light sources are tunable lasers. However, many measurements require a tuning range that is beyond the range that can be achieved by a single gain chip in the laser. Prior art solutions for limited tuning range have been proposed. One class of solutions expands the amplification range of the laser gain section by processing light in series with multiple gain chips, each providing amplification in a respective wavelength band. These solutions have problems associated with the non-active gain chip absorbing light amplified by another chip.

Other solutions utilize gain chips with multiple active layers, each providing gain in a different spectral range. These solutions suffer from the problem that multiple active layers provide gain simultaneously.

Disclosure of Invention

The invention includes a laser module having a plurality of component lasers, each component laser characterized by a gain chip, a diffraction grating structure, a pivot point, and an output laser beam traveling in an output beam direction. A drive shaft is coupled to each pivot point and rotates each diffraction grating structure about the pivot point associated with the constituent laser. The laser module also includes a plurality of reflectors, each reflector positioned to receive an output laser beam from one of the plurality of component lasers and direct the output laser beam along an output path common to all of the component laser beams. The controller controls the rotation angle of the drive shaft.

In one aspect of the invention, the diffraction grating structures of a plurality of component lasers are positioned such that no more than one of the component lasers lase for any given angle of rotation of the drive axis.

In another aspect of the invention, one of the reflectors comprises a partial mirror.

In another aspect of the invention, one of the reflectors comprises a binaural reflector that reflects light generated by a respective one of the constituent lasers and passes light generated by the other constituent laser.

In another aspect of the invention, one of the reflectors is rotated about an axis on the reflector such that the reflector does not block light along the output path, the rotation being controlled by the controller.

In another aspect of the invention, one of the component lasers includes first and second diffraction gratings having different grating pitches positioned such that, for any given rotation of the diffraction grating structure about the pivot point, at most one diffraction grating reflects light from a gain chip in the component laser.

Drawings

Fig.1 shows a component laser according to one embodiment of the present invention.

Figure 2 is a side view of one embodiment of a laser module according to the present invention.

Fig.3 is a side view of a laser module according to another embodiment of the present invention.

Figure 4 shows a component laser with two gratings.

Detailed Description

The present invention solves the above problems by providing a laser module that is made up of a plurality of constituent lasers that are tuned together. Referring now to fig.1, a component laser is shown according to one embodiment of the present invention. The component laser 10 includes a gain chip 11 and a grating 16 that provides a wavelength selective filter for light amplified by the gain chip 11. The gain chip 11 has a reflective coating at end 12 and an anti-reflection coating at end 13. Light from the gain chip 11 is expanded by the lens 14 into a beam 15 and directed to the diffraction grating 60. The light diffracted back to the gain chip 11 is in a narrow band determined by the angle between the gradient and the beam 15. Light reflected from the grating as beam 17 is reflected by a mirror 18 at right angles to the grating 16. Light reflected from mirror 18 is directed along path 19 to reflector 12, which reflects the light in a direction perpendicular to the plane of the drawing.

The grating 12 and the mirror 18 are structurally connected together so that they move together about an axis 21 perpendicular to the plane of the drawing. The component laser 10 is tuned by rotating the grating 12 and mirror 18 about axis 21. The grating 16 has an angular range over which the constituent lasers 10 will lase. When the grating 16 is rotated out of this range, the constituent lasers 10 will cease to lase.

To simplify the following discussion, a component laser will be defined as a laser having a gain chip and a diffraction grating, wherein the diffraction grating is mounted in a grating structure comprising a flat mirror mounted at right angles to the plane of the diffraction grating, such that the diffraction grating and the flat mirror are fixed relative to each other and rotate together about a pivot point, such that light reflected from the diffraction grating back to the gain chip has a wavelength that depends on the angle between the plane of the diffraction grating and the path from the gain chip to the diffraction grating, and light reflected from the flat mirror forms an output beam from the component laser.

Reference is now made to fig.2, which is a side view of one embodiment of a laser module 30 according to the present invention. The individual component lasers are shown at 31, 32 and 33. The individual reflectors corresponding to the component lasers 31-33 are shown at 25-27, respectively. In the example shown in the figure, the constituent laser 33 is lasing and producing an output beam 27A. When each laser module emits laser light, the corresponding output beam coincides with beam 27A. The angle of rotation of each grating making up the laser is controlled by a motor 29, which is controlled by a controller 35 which sets the angle of the grating to correspond to the wavelength specified by the user by setting the angle of rotation of the shaft 28.

In one exemplary embodiment, the angles of the gratings in the component lasers are set such that for any given angle of rotation of the shaft 28, only one grating is positioned to emit laser light. The individual gain chips and starting grating positions are selected so that the output wavelength varies continuously with the angle of rotation of the shaft 28.

In another exemplary embodiment, the gradient angles in the constituent lasers and the gain chip are selected such that two of the constituent lasers have overlapping operating ranges. As the angle of the shaft changes, the first constituent laser begins lasing at the beginning of its operating range at a wavelength that the second constituent laser also provides at the end of its operating range.

In the above embodiments, the output beam from each component laser is directed along a common path by a reflector that is part of that component laser, and therefore the output of the laser module appears to be from a single laser. For example, reflector 26 must pass the light produced by the constituent lasers 31. In an exemplary embodiment, the reflector is either a partial mirror or a dichotic reflector.

In another exemplary embodiment, the mirrors are hinged such that each mirror flips into position when its constituent laser gratings are positioned to the laser and each mirror flips out of the path when the laser module is no longer emitting laser light. Reference is now made to fig.3, which is a side view of a laser module 40 according to another embodiment of the present invention. Laser module 40 differs from laser module 30 shown in fig.2 in that reflectors 25-27 have been replaced by movable reflectors 45-47. Each movable reflector pivots about axis 49 between a vertical position in which the reflector does not intercept light from the constituent lasers above it in the stack, and a 45 degree orientation in which the reflector reflects light from the respective constituent laser and directs it in a downward direction. Reflector 45, which makes up laser 41, is at a 45 degree orientation, while

reflectors

46 and 47, which make up

lasers

42 and 43, respectively, are in a vertical position. The angle of rotation of the shaft 28 or controller 35 may control which reflector is positioned to deflect light from its constituent laser. In this configuration, the total reflection mirror can be used as a reflector as long as only one constituent laser is operating at a time.

In the above embodiment, only one constituent laser emits laser light at a time. However, embodiments in which two or more lasers simultaneously generate light may also be constructed. Such a light source may provide light of various wavelengths that may be used for raman scattering or other spectroscopic measurements.

In embodiments where not all lasers are producing light at the same time, it may still be advantageous to power the gain chip in a laser that is not producing laser light. This will keep the temperature of all gain chips at their operating temperature, thereby preventing shifts and wavelengths due to temperature changes as the gain chips heat up.

For some applications it may be advantageous to provide lasers with different grating pitches, even for the same gain chip. Changing the grating pitch changes the line width of the laser generated spectrum. Thus, if a particular application requires tunable lasers with different spectral widths, constituent lasers with different grating pitches may be used. In one embodiment, the grating pitch of the different constituent lasers is different. In such an embodiment, two component lasers with the same gain chip but different grating pitches may be utilized. However, this requires an additional component laser. Alternatively, a single component laser with multiple gratings may be provided.

In the above embodiments, each component laser comprises a single grating and its corresponding reflector mounted at 90 ° to the plane of the grating. However, embodiments using multiple gratings in a constituent laser may also be constructed. Referring now to fig.4, a component laser having two gratings is shown. In this example, the second grating 88 is mounted at right angles to the plane of the grating 16 shown in FIG. 1. The back surface of grating 16 acts as a reflector for grating 88. Grating 88 is introduced into the optical path by rotating the grating structure about axis 21 in a manner similar to that described above.

The above-described embodiment has a specific number of composite lasers, i.e., three. However, it should be understood that the number of composite lasers is not limited to three.

The above-described embodiments of the present invention have been provided to illustrate various aspects of the present invention. However, it is to be understood that different aspects of the present invention, shown in different specific embodiments, may be combined to provide other embodiments of the present invention. In addition, various modifications to the present invention will become apparent from the foregoing description and accompanying drawings. Accordingly, the invention is not to be restricted except in light of the attached claims.

Claims

1. A laser module, comprising:

a plurality of component lasers, each of the plurality of component lasers characterized by a gain chip, a diffraction grating structure, a pivot point, and an output laser beam traveling in an output beam direction;

a drive shaft coupled to each of the pivot points, the drive shaft rotating each of the diffraction grating structures about the pivot point associated with that component laser;

a plurality of reflectors, each of the plurality of reflectors positioned to receive the output laser beam from one of the plurality of component lasers and direct the output laser beam along an output path common to all of the component laser beams; and

a controller that controls a rotation angle of the drive shaft.

2. The laser module of claim 1, wherein the diffraction grating structures of the plurality of component lasers are positioned such that no more than one component laser of the plurality of component lasers fires light for any given angle of rotation of the drive axis.

3. The laser module of claim 1, wherein one of the plurality of reflectors comprises a partial mirror.

4. The laser module of claim 1, wherein one of the plurality of reflectors comprises a dichroic reflector that reflects light produced by a respective one of the plurality of constituent lasers and passes light produced by another one of the plurality of constituent lasers.

5. The laser module of claim 1, wherein one of the plurality of reflectors rotates about an axis on the reflector such that the one of the plurality of reflectors does not block light along the output path, the rotation being controlled by the controller.

6. The laser module of claim 1 wherein one of the plurality of component lasers includes first and second diffraction gratings having different grating pitches, the first and second diffraction gratings positioned such that for any given rotation of the diffraction grating structure about the pivot point, at most one of the diffraction gratings reflects light from the gain chip in the component laser.