High-precision testing device for testing frequency modulation response of semiconductor laser

Abstract

A testing device for high-precision testing of frequency modulation response of a semiconductor laser is provided with a current square wave generator and a light beam splitter, a current output port of the current square wave generator is connected with a current input port of a to-be-tested laser, and a laser input port of the light beam splitter is connected with a laser output port of the to-be-tested laser. A first laser output port of the light beam splitter is connected with a first laser input port of the light beam combiner, a second laser output port of the light beam splitter is connected with a laser input port of the light delayer, a laser output port of the light delayer is connected with a second laser input port of the light beam combiner, and a laser output port of the light beam combiner is connected with a laser input port of the light detector. And a light current signal output port of the light detector is connected with an electric signal input port of the data processor. According to the testing device, the MHz-level testing precision can be realized, the use of a reference laser is avoided, the complexity of a testing system and a testing scheme is reduced, the use of a high-precision spectrograph is avoided, the testing cost is reduced, and the testing precision is improved.

Description

Technical Field

[0001] The utility model relates to a semiconductor laser, in particular to a testing device for testing the semiconductor laser. Background Art

[0002] There are many types of semiconductor lasers, and the frequency modulation response of different semiconductor lasers—that is, the relationship between the output laser frequency and the injection current intensity—needs to be experimentally determined. There are two traditional testing approaches. One uses a spectrometer. This involves varying the injected photocurrent intensity of the semiconductor laser while reading the output laser frequency with the spectrometer to determine the relationship between the output laser frequency and the injected current intensity. While this approach is relatively simple to implement, its accuracy is highly dependent on the spectral resolution of the spectrometer. Typically, spectrometers have a spectral resolution of less than 10 GHz, making this approach limited to rough testing of semiconductor lasers. Another approach involves using two identical semiconductor lasers for beat frequency measurement. This involves injecting a steady current into a reference laser while continuously varying the injection current intensity of the semiconductor laser under test. The two laser beams are then mixed using an optical beam combiner. A photodetector then converts the mixed optical signal into a photocurrent signal. Finally, a data processor performs a Fourier transform on the photocurrent signal, calculating the frequency difference between the reference laser and the semiconductor laser under test. This allows the relationship between the output laser frequency and the injected current intensity of the semiconductor laser under test to be derived. On the one hand, this solution requires a reference laser, which complicates the test system. On the other hand, this solution requires adjusting the reference laser to be close to the semiconductor laser to be tested before testing, which makes the test solution more complicated. Utility Model Content

[0003] The purpose of the utility model is to provide a test device for testing the frequency modulation response of a semiconductor laser with high precision, which can meet the requirements of high precision testing and overcome the problems caused by using a reference laser.

[0004] The utility model is implemented as follows: a test device for high-precision testing of the frequency modulation response of a semiconductor laser is provided with a current square wave generator with adjustable output current, an optical beam splitter, an optical delay device, a photosynthetic beam combiner, a light detector and a data processor, the current output port of the current square wave generator is connected to the current input port of the semiconductor laser to be tested, the laser input port of the optical beam splitter is connected to the laser output port of the semiconductor laser to be tested, the optical beam splitter has a first laser output port and a second laser output port, the optical beam splitter divides a laser beam input into two laser beams with equal power, which are output from the first laser output port and the second laser output port respectively, the first laser output port of the optical beam splitter is connected to the first laser input port of the photosynthetic beam combiner, the second laser output port of the optical beam splitter is connected to the laser input port of the optical delay device, the laser output port of the optical delay device is connected to the second laser input port of the photosynthetic beam combiner, the laser output port of the photosynthetic beam combiner is connected to the laser input port of the light detector, and the photocurrent signal output port of the light detector is connected to the electrical signal input port of the data processor.

[0005] As a best implementation, the duty cycle of the square wave current signal output by the current square wave generator is 1 / 2.

[0006] The operating principle of the test device is as follows: a square wave current signal output by a current square wave generator is injected into the semiconductor laser under test, which then emits a square wave-modulated laser beam. This laser beam is then split into two beams of equal power by an optical beam splitter. One laser beam enters the photosynthetic combiner directly, while the other laser beam passes through an optical delay device before entering the photosynthetic combiner. The two laser beams are mixed in the photosynthetic combiner. A photodetector converts the mixed laser beams into a photocurrent signal. Finally, a data processor performs a Fourier transform on this photocurrent signal and calculates the maximum value of the frequency domain data, thereby determining the relationship between the frequency of the laser output from the semiconductor laser under test and the injection current intensity.

[0007] The advantages of the present invention are: 1. The delayed self-coherence test based on square wave injection current can achieve MHz-level test accuracy; 2. It avoids the use of a reference laser, reducing the complexity of the test system and test plan; 3. It avoids the use of a high-precision spectrometer, reducing test costs while improving test accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a structural schematic diagram of an embodiment of the present utility model. DETAILED DESCRIPTION

[0009] To facilitate understanding of the present invention, the present invention is described more fully below through examples. The examples provide embodiments of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in the examples.

[0010] It should be noted that the "first" and "second" mentioned in the present invention are only used to distinguish names and do not represent specific quantities and orders.

[0011] See also Figure 1 The test device for high-precision testing of the frequency modulation response of a semiconductor laser mainly consists of a current square wave generator with adjustable output current, an optical beam splitter, an optical delay device, an optical beam combiner, a photodetector, and a data processor. The current output port of the current square wave generator is connected to the current input port of the semiconductor laser under test. The current square wave generator outputs a square wave current signal that is injected into the semiconductor laser under test, causing the semiconductor laser under test to emit square-wave modulated laser light. The laser output port of the semiconductor laser under test is connected to the laser input port of the optical beam splitter. The optical beam splitter has a first laser output port and a second laser output port. The first laser output port is connected to the first laser input port of the optical beam combiner, and the second laser output port is connected to the laser input port of the optical delay device. The optical beam splitter splits the laser beam emitted by the semiconductor laser under test into two laser beams of equal power, which are respectively sent to the optical beam combiner and the optical delay device. The laser output port of the optical delay device is connected to the second laser input port of the optical beam combiner. The laser light directly sent from the optical beam splitter and the laser light output through the optical delay device are mixed in the optical beam combiner. The laser output port of the optical beam combiner is connected to the laser input port of the photodetector, which converts the mixed laser beam into a photocurrent signal. The photocurrent signal output port of the photodetector is connected to the electrical signal input port of the data processor. The data processor performs a Fourier transform and calculates the maximum value of the frequency domain data on the photocurrent signal sent by the photodetector. It calculates the frequency difference between the two laser beams output from the optical beam splitter, and thus derives the relationship between the output frequency of the semiconductor laser under test and the injection current intensity, that is, obtains the frequency modulation response of the semiconductor laser under test.

[0012] A current square wave generator with adjustable output current can be constructed using conventional devices or components, such as signal generators and function generators. A beam combiner is a commonly used fiber optic device that combines two laser beams into a single beam. A photodetector is a commonly used optoelectronic device that uses the photoelectric effect to convert laser input into a photocurrent signal output. Computers, microcontrollers, CPUs, or FPGAs can all be used as data processors.

[0013] When using the test device described in the present invention, the duty cycle of the square wave current signal output by the current square wave generator is preferably set to 1 / 2. If other duty cycles are used, noise will be introduced and the effect will be degraded. The low-level current value and the high-level current value of the square wave current signal output by the current square wave generator are both adjustable, and during measurement, one of the low-level current value and the high-level current value should be adjusted to be constant equal to a typical injection current value calibrated by the manufacturer of the laser to be tested for the laser to be tested, and the current value of the other level is the variation that needs to be adjusted during the measurement process. For example, if the low-level current value output by the current square wave generator is adjusted to be constant equal to a typical injection current value calibrated by the manufacturer, then the high-level current value output by the current square wave generator is the variation that needs to be adjusted during the measurement process; conversely, if the high-level current value output by the current square wave generator is adjusted to be constant equal to a typical injection current value calibrated by the manufacturer, then the low-level current value output by the current square wave generator is the variation that needs to be adjusted during the measurement process. During the measurement process, each time the current square wave generator adjusts the variation, the data processor uses the determined variation as the current value injected into the laser under test, thereby calculating the laser frequency of the laser under test corresponding to that current value. By repeatedly adjusting the variation multiple times, each time to a different current value, the relationship between the laser frequency of the laser under test and the injection current intensity can be determined. The specific algorithm of the data processor can refer to the algorithm used in existing methods using a reference laser for measurement.

Claims

1. A test device for high-precision testing of the frequency modulation response of a semiconductor laser, characterized by: The invention is provided with a current square wave generator with adjustable output current, an optical beam splitter, an optical delay device, an optical beam combiner, a light detector and a data processor. The current output port of the current square wave generator is connected to the current input port of the semiconductor laser to be measured, the laser input port of the optical beam splitter is connected to the laser output port of the semiconductor laser to be measured, the optical beam splitter has a first laser output port and a second laser output port, the optical beam splitter divides a laser beam input into two laser beams with equal power and outputs them from the first laser output port and the second laser output port respectively, the first laser output port of the optical beam splitter is connected to the first laser input port of the optical beam combiner, the second laser output port of the optical beam splitter is connected to the laser input port of the optical delay device, the laser output port of the optical delay device is connected to the second laser input port of the optical beam combiner, the laser output port of the optical beam combiner is connected to the laser input port of the light detector, and the photocurrent signal output port of the light detector is connected to the electrical signal input port of the data processor.

2. The high-precision test device for testing the frequency modulation response of a semiconductor laser according to claim 1, wherein: The duty cycle of the square wave current signal output by the current square wave generator is 1 / 2.

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