CN117740148A - System and method for measuring laser spectrum of external cavity laser - Google Patents

Abstract

There is provided a method of measuring an external cavity laser lasing spectrum comprising: placing the external cavity laser to be tested on a displacement table with a temperature control function; loading an alternating current source output current to a laser, and controlling the temperature to be a set temperature; the method comprises the steps that a light beam emitted by a laser is incident to a grating through a focusing lens and then fed back to the laser to obtain an output light beam; receiving the output light beam through a spectrometer detector for spectrum scanning; the method comprises the steps of connecting an alternating frequency reference signal of an alternating current source to a reference signal interface of a phase-locked amplifier, and connecting an output signal of a spectrometer detector to an input interface of the phase-locked amplifier; the position of the external cavity laser is finely adjusted through the displacement table, so that the indication of the lock-in amplifier is maximum; rotating the grating by using an electric control angular displacement table to change the incidence angle of the light beam emitted by the external cavity laser to the grating; and after each rotation of the electronic control angular displacement table, controlling a spectrometer detector to perform spectrum scanning and store data, and finally measuring the high-precision laser spectrum of the external cavity laser.

Description

System and method for measuring laser spectrum of external cavity laser

Technical Field

The disclosure relates to the technical field of lasers and spectrum testing thereof, in particular to a system and a method for measuring laser spectrum of an external cavity laser with high accuracy.

Background

The tunable grating external cavity semiconductor laser is mainly divided into Littrow and Littman structures, in the Littrow structure external cavity semiconductor laser, light beams generated by an active area are collimated by a collimating lens and then are incident into a blazed grating to be diffracted, first-order diffracted light generated by diffraction is fed back to the active area of a gain device along an incident light path, a new resonant cavity is formed by the grating and the front end face of the device, and wavelength tuning is realized by rotating the grating. In the Littman type external cavity semiconductor laser, first-order diffraction light generated by a blazed grating is projected to a reflecting mirror, then the first-order diffraction light is reflected back to the grating by the reflecting mirror, and then the first-order diffraction light is fed back to an active area of a gain device by the grating, and the output wavelength is tuned by rotating the reflecting mirror. In the Littman structure, laser is diffracted twice by the grating, and more grating lines can be covered by the larger angle of incidence to the grating, so that the laser line width is narrower than that of the Littrow structure. In addition, the zero-order light emitting direction in the Littman structure does not change along with the tuning of the wavelength, and is beneficial to the collection of optical power. However, the larger incident angle in the Littman structure can reduce the diffraction efficiency of the grating, and the added reflector can bring about certain power loss. Therefore, the Littrow structure is adopted, so that the output power is larger, the structure is simpler, and the tuning is more convenient.

In the Littrow structure, the existing scheme adopts a grating spectrometer and a CCD detection means to directly measure the spectrum of the external cavity laser, the spectrum signal is easy to receive external interference, and the spectrum precision is closely related to the CCD resolution. CCDs that typically operate at room temperature cannot meet the requirements of high-precision spectral testing.

Disclosure of Invention

First, the technical problem to be solved

Based on the above problems, the present disclosure provides a system and a method for measuring an external cavity laser lasing spectrum, so as to alleviate the technical problems that in the prior art, spectrum signals are easy to interfere with external noise and shake, in addition, the accuracy of a test spectrum has a direct relationship with the resolution of a CCD, and a CCD working at room temperature cannot meet the high-precision spectrum test requirement.

(II) technical scheme

In one aspect of the present disclosure, there is provided a method of measuring an external cavity laser lasing spectrum comprising operations S1-S8: wherein:

operation S1: placing the external cavity laser to be tested on a displacement table with a temperature control function;

operation S2: loading an alternating current source output current to a laser, and controlling the temperature to be a set temperature;

operation S3: the method comprises the steps that a light beam emitted by a laser is incident to a grating through a focusing lens and then fed back to the laser to obtain an output light beam;

operation S4: receiving the output light beam through a spectrometer detector for spectrum scanning;

operation S5: the method comprises the steps of connecting an alternating frequency reference signal of an alternating current source to a reference signal interface of a phase-locked amplifier, and connecting an output signal of a spectrometer detector to an input interface of the phase-locked amplifier;

operation S6: the position of the external cavity laser is finely adjusted through the displacement table, so that the indication of the lock-in amplifier is maximum;

operation S7: rotating the grating by using an electric control angular displacement table to change the incidence angle of the light beam emitted by the external cavity laser to the grating according to a set angle; and

operation S8: and after each rotation of the electronic control angular displacement table, controlling a spectrometer detector to perform spectrum scanning and store data, and finally measuring the high-precision laser spectrum of the external cavity laser.

According to the embodiment of the disclosure, the displacement table with the temperature control function is a five-axis displacement table.

According to an embodiment of the present disclosure, the method for measuring the laser spectrum of the external cavity laser further includes adjusting the focusing lens position to maximize the lock-in amplifier index.

According to the embodiment of the disclosure, the incidence angle of the light beam emitted by the external cavity laser to the grating is changed at intervals of 0.1 degrees.

According to an embodiment of the present disclosure, the spectrometer detector is a reflective grating spectrometer detector.

According to an embodiment of the present disclosure, the set temperature is 20 degrees celsius.

According to the embodiment of the disclosure, the electronic control angular displacement table and/or the displacement table with the temperature control function are repeatedly controlled, the spectrum scanning is repeatedly performed, and the acquisition and the processing of the scanning data are performed by utilizing the acquisition computer.

According to the embodiment of the disclosure, after the spectrum scanning data is processed by the lock-in amplifier, the laser spectrum of the external cavity laser is finally obtained.

According to the embodiment of the disclosure, the control of the displacement table and the acquisition of the spectrum scanning data are completed through a self-programming labview program.

In another aspect of the present disclosure, a system and a method for measuring an external cavity laser lasing spectrum are provided for implementing the method of any of the above, the system comprising: the five-axis displacement table has a temperature control function; an alternating current source for loading an output current onto the laser; the focusing lens focuses and irradiates the light beam emitted by the laser to the grating, and the light beam is fed back to the laser after being diffracted by the grating to obtain an output light beam; the electric control angular displacement table is used for rotating the angle of the grating; the spectrometer detector receives the output light beam for spectral scanning; the phase-locked amplifier receives an alternating frequency reference signal of the alternating current source through a reference signal interface, and an input interface of the phase-locked amplifier is connected to the spectrometer detector and receives an output signal of the spectrometer detector; the position of the external cavity laser is finely adjusted through the five-axis displacement table, the phase-locked amplifier is enabled to be the largest in indication, the electric control angular displacement table is utilized to rotate the grating, the incidence angle of a light beam emitted by the external cavity laser to the grating is enabled to change according to a set angle, after each time of rotating the electric control angular displacement table, the spectrometer detector is controlled to conduct spectrum scanning and store data, and finally the high-precision laser spectrum of the external cavity laser is measured.

(III) beneficial effects

As can be seen from the above technical solutions, the system and method for measuring the lasing spectrum of an external cavity laser according to the present disclosure have at least one or a part of the following advantages:

(1) The phase-locked amplification technology is introduced to combine the characteristics of the reflection grating spectrometer, so that the problems of low spectral resolution and high noise of the external cavity laser in the prior art are overcome;

(2) The TE temperature control is directly combined with the five-axis adjusting displacement table, so that on one hand, the laser can be cooled, and in addition, the spatial position (xyz) and the pitching angle and the rotating angle of the outer cavity laser chip can be accurately adjusted through the five-axis adjusting displacement table, and the outer cavity laser can be more accurately incident on the grating at a blazing angle;

(3) The grating can be precisely rotated.

Drawings

Fig. 1 is a schematic diagram of a system for measuring an external cavity laser lasing spectrum according to an embodiment of the disclosure.

Fig. 2 is a flow chart of a method of measuring an external cavity laser lasing spectrum according to an embodiment of the disclosure.

Fig. 3 is a schematic diagram of a laser spectrum of a 1.55 micron InP quantum dot external cavity laser chip measured according to an embodiment of the present disclosure.

Fig. 4 is a flowchart illustrating a specific procedure for measuring an external cavity laser lasing spectrum according to an embodiment of the disclosure.

Detailed Description

The invention provides a system and a method for measuring the laser spectrum of an external cavity laser, which overcome the problems of low spectral resolution and large noise of the external cavity laser in the prior art by introducing the characteristics of a phase-locked amplification technology and a reflection grating spectrometer.

For the purposes of promoting an understanding of the principles and advantages of the disclosure, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same.

In an embodiment of the present disclosure, a method for measuring an external cavity laser lasing spectrum is provided, as shown in fig. 2, 4 and 1, the method including operations S1-S8, wherein:

operation S1: placing the external cavity laser to be tested on a displacement table with a temperature control function;

operation S2: loading an alternating current source output current to a laser, and controlling the temperature to be a set temperature;

operation S3: the method comprises the steps that a light beam emitted by a laser is incident to a grating through a focusing lens and then fed back to the laser to obtain an output light beam;

operation S4: receiving the output light beam through a spectrometer detector for spectrum scanning;

operation S5: the method comprises the steps of connecting an alternating frequency reference signal of an alternating current source to a reference signal interface of a phase-locked amplifier, and connecting an output signal of a spectrometer detector to an input interface of the phase-locked amplifier;

operation S6: the position of the external cavity laser is finely adjusted through the displacement table, so that the indication of the lock-in amplifier is maximum;

operation S7: rotating the grating by using an electric control angular displacement table to change the incidence angle of the light beam emitted by the external cavity laser to the grating according to a set angle; and

operation S8: and after each rotation of the electronic control angular displacement table, controlling a spectrometer detector to perform spectrum scanning and store data, and finally measuring the high-precision laser spectrum of the external cavity laser.

More specifically, an acquisition computer, a lock-in amplifier, a spectrometer, an alternating current source, a laser temperature control device and an electric angular displacement table controller are turned on. And placing an external cavity laser chip to be tested, and loading the output current of the alternating current source onto the laser chip by using the probe. And waiting for temperature control to be stable, and controlling the temperature at 20 ℃. The alternating current source alternating frequency reference signal is connected to the phase-locked amplifier reference signal interface, and the output signal of the spectrometer detector is connected to the phase-locked amplifier input interface. And fine-tuning the position of the external cavity laser chip by using the five-axis displacement table to maximize the index of the lock-in amplifier, adjusting the position of the focusing lens, and repeatedly adjusting the position of the external cavity laser chip to maximize the index of the lock-in amplifier. The electric control angular displacement table is utilized to rotate the grating, so that the incidence angle of the light beam emitted by the external cavity laser chip to the grating changes, and at the moment, the electric control angular displacement table rotates once every 0.1 degree, namely, the incidence angle of the light beam emitted by the external cavity laser to the grating changes once every 0.1 degree. After each rotation of the electric control angular displacement table, the spectrometer is controlled to perform spectrum scanning by using the acquisition computer, and data are stored. And repeatedly rotating the electric control angular displacement table, and repeatedly performing spectrum scanning. And (3) carrying out data acquisition and processing on the spectrum scanning data by using an acquisition computer after processing by using a lock-in amplifier, and finally obtaining the high-precision laser spectrum of the external cavity laser chip.

In the present disclosure, an InP quantum dot external cavity laser chip of 1.55 microns is taken as an example, and after the system test, an external cavity laser 1. The present disclosure innovatively introduces a lock-in amplifier as a reprocessing tool for spectrum signals, which can reduce noise and improve sensitivity. Because the external cavity laser chip testing process requires accurate control on the incident angle, the grating rotation position and the like, the external cavity laser chip testing process is accurately controlled on the external cavity laser chip and the grating position by utilizing a plurality of five-axis displacement tables and an electric control angular displacement table. The spectrometer in the present disclosure is selected from a common reflection grating spectrometer and a single-point detector, which are cheaper than the existing CCD area array detector. All electric control and data acquisition related in the disclosure are controlled in real time by using labview system, and can be operated automatically by one key.

The present disclosure provides a system for measuring an external cavity laser lasing spectrum, as shown in fig. 1, the system comprising:

the five-axis displacement table has a temperature control function;

an alternating current source for loading an output current onto the laser;

the focusing lens focuses and irradiates the light beam emitted by the laser to the grating, and the light beam is fed back to the laser after being diffracted by the grating to obtain an output light beam;

the electric control angular displacement table is used for rotating the angle of the grating;

the spectrometer detector receives the output light beam for spectral scanning;

the phase-locked amplifier receives an alternating frequency reference signal of the alternating current source through a reference signal interface, and an input interface of the phase-locked amplifier is connected to the spectrometer detector and receives an output signal of the spectrometer detector;

the position of the external cavity laser is finely adjusted through the five-axis displacement table, the phase-locked amplifier is enabled to be the largest in indication, the electric control angular displacement table is utilized to rotate the grating, the incidence angle of a light beam emitted by the external cavity laser to the grating is enabled to change according to a set angle, after each time of rotating the electric control angular displacement table, the spectrometer detector is controlled to conduct spectrum scanning and store data, and finally the high-precision laser spectrum of the external cavity laser is measured.

According to the embodiment of the disclosure, the control of the displacement table and the acquisition of the spectrum scanning data are completed through a self-programming labview program.

Thus, embodiments of the present disclosure have been described in detail with reference to the accompanying drawings. It should be noted that, in the drawings or the text of the specification, implementations not shown or described are all forms known to those of ordinary skill in the art, and not described in detail. Furthermore, the above definitions of the elements and methods are not limited to the specific structures, shapes or modes mentioned in the embodiments, and may be simply modified or replaced by those of ordinary skill in the art.

From the foregoing description, one skilled in the art will readily recognize the system and method of measuring the lasing spectrum of an external cavity laser of the present disclosure.

In summary, the present disclosure provides a system and a method for measuring an external cavity laser emission spectrum, and compared with the prior art that an optical fiber spectrometer and a CCD detector are mostly used to detect the external cavity spectrum, the method for manufacturing the external cavity laser emission spectrum has the problems of large noise and low detection accuracy affected by the CCD. The method utilizes the frequency signal generated by the alternating current source to combine with the phase-locked amplification technology, and utilizes the modes of the reflection type spectrometer and the single-point detector to realize the accurate test of the laser spectrum of the high-precision external cavity laser chip. The position of the external cavity laser chip and the position of the grating in the optical path can be accurately controlled by adopting a plurality of five-axis displacement tables and electric angular displacement tables for combined use so as to facilitate the accurate control of the positions of the external cavity laser chip and the grating in the test process, thereby realizing the efficient lasing of the external cavity laser chip. All the electric control systems and data acquisition devices in the present disclosure complete related control and data acquisition by means of self-programmed labview programs.

It should also be noted that the foregoing describes various embodiments of the present disclosure. These examples are provided to illustrate the technical content of the present disclosure, and are not intended to limit the scope of the claims of the present disclosure. A feature of one embodiment may be applied to other embodiments by suitable modifications, substitutions, combinations, and separations.

It should be noted that in this document, having "an" element is not limited to having a single element, but may have one or more elements unless specifically indicated.

In addition, unless specifically stated otherwise, herein, "first," "second," etc. are used for distinguishing between multiple elements having the same name and not for indicating a level, a hierarchy, an order of execution, or a sequence of processing. A "first" element may occur together with a "second" element in the same component, or may occur in different components. The presence of an element with a larger ordinal number does not necessarily indicate the presence of another element with a smaller ordinal number.

In this context, the so-called feature A "or" (or) or "and/or" (and/or) feature B, unless specifically indicated, refers to the presence of B alone, or both A and B; the feature A "and" (and) or "AND" (and) or "and" (and) feature B, means that the nail and the B coexist; the terms "comprising," "including," "having," "containing," and "containing" are intended to be inclusive and not limited to.

Further, in this document, terms such as "upper," "lower," "left," "right," "front," "back," or "between" are used merely to describe relative positions between elements and are expressly intended to encompass situations of translation, rotation, or mirroring. In addition, in this document, unless specifically indicated otherwise, "an element is on another element" or similar recitation does not necessarily mean that the element contacts the other element.

Furthermore, unless specifically described or steps must occur in sequence, the order of the above steps is not limited to the list above and may be changed or rearranged according to the desired design. In addition, the above embodiments may be mixed with each other or other embodiments based on design and reliability, i.e. the technical features of the different embodiments may be freely combined to form more embodiments.

While the foregoing embodiments have been described in some detail for purposes of clarity of understanding, it will be understood that the foregoing embodiments are merely illustrative of the invention and are not intended to limit the invention, and that any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the present disclosure are intended to be included within the scope of the present disclosure.

Claims (10)

1. A method of measuring an external cavity laser lasing spectrum comprising:

operation S1: placing the external cavity laser to be tested on a displacement table with a temperature control function;

operation S2: loading an alternating current source output current to a laser, and controlling the temperature to be a set temperature;

operation S3: the method comprises the steps that a light beam emitted by a laser is incident to a grating through a focusing lens and then fed back to the laser to obtain an output light beam;

operation S4: receiving the output light beam through a spectrometer detector for spectrum scanning;

operation S5: the method comprises the steps of connecting an alternating frequency reference signal of an alternating current source to a reference signal interface of a phase-locked amplifier, and connecting an output signal of a spectrometer detector to an input interface of the phase-locked amplifier;

operation S6: the position of the external cavity laser is finely adjusted through the displacement table, so that the indication of the lock-in amplifier is maximum;

operation S7: rotating the grating by using an electric control angular displacement table to change the incidence angle of the light beam emitted by the external cavity laser to the grating according to a set angle; and

operation S8: and after each rotation of the electronic control angular displacement table, controlling a spectrometer detector to perform spectrum scanning and store data, and finally measuring the high-precision laser spectrum of the external cavity laser.

2. The method for measuring the lasing spectrum of an external cavity laser as claimed in claim 1, wherein the displacement stage with temperature control function is a five-axis displacement stage.

3. The method of measuring the lasing spectrum of an external cavity laser as claimed in claim 1, further comprising adjusting a focusing lens position to maximize the lock-in amplifier reading.

4. The method of measuring the lasing spectrum of an external cavity laser as claimed in claim 1, wherein the angle of incidence of the beam of light emitted by the external cavity laser onto the grating is varied once every 0.1 °.

5. The method of measuring the lasing spectrum of an external cavity laser as claimed in claim 1, said spectrometer detector being a reflective grating spectrometer detector.

6. The method of measuring the lasing spectrum of an external cavity laser as claimed in claim 1, said set temperature being 20 degrees celsius.

7. The method for measuring the laser spectrum of the external cavity laser according to claim 1, wherein the electronic control angular displacement table and/or the displacement table with the temperature control function are/is repeatedly controlled, the spectrum scanning is repeatedly performed, and the acquisition and the processing of scanning data are performed by using an acquisition computer.

8. The method for measuring the lasing spectrum of an external cavity laser as claimed in claim 7, wherein the spectral scan data is processed by a lock-in amplifier to obtain the lasing spectrum of the external cavity laser.

9. The method for measuring laser emission spectrum of external cavity laser according to claim 8, wherein the control of displacement stage and the acquisition of spectrum scan data are completed by self-programming labview program.

10. A system for measuring the laser emission spectrum of an external cavity laser for implementing the method of any of claims 1-9, the system comprising:

the five-axis displacement table has a temperature control function;

an alternating current source for loading an output current onto the laser;

the focusing lens focuses and irradiates the light beam emitted by the laser to the grating, and the light beam is fed back to the laser after being diffracted by the grating to obtain an output light beam;

the electric control angular displacement table is used for rotating the angle of the grating;

the spectrometer detector receives the output light beam for spectral scanning;

the phase-locked amplifier receives an alternating frequency reference signal of the alternating current source through a reference signal interface, and an input interface of the phase-locked amplifier is connected to the spectrometer detector and receives an output signal of the spectrometer detector;

the position of the external cavity laser is finely adjusted through the five-axis displacement table, the phase-locked amplifier is enabled to be the largest in indication, the electric control angular displacement table is utilized to rotate the grating, the incidence angle of a light beam emitted by the external cavity laser to the grating is enabled to change according to a set angle, after each time of rotating the electric control angular displacement table, the spectrometer detector is controlled to conduct spectrum scanning and store data, and finally the high-precision laser spectrum of the external cavity laser is measured.