Device for measuring linewidth of narrow linewidth laser based on optical fiber time-delay self heterodyne method as well as method for measuring thereof

Abstract

The invention discloses a device of measuring the line-width of a laser with narrow line-width and a method of measuring the line-width based on a optical fiber delay self-heterodyne method; in the hardware device, an optical fiber delay line is connected between a first and a second couplers; an acousto-optic modulator is connected between the first and the second couplers; the measured laser isconnected to the input of the first coupler, and a photoelectric detector is connected to the output of the second coupler; the photoelectric detector is connected with a spectrum analyzer. In the line-width measurement, simulation models of the line-width triangle v of the laser and the spectrum-width triangle f of the photoelectric current heterodyne signal are built in the frequency shift delay self-heterodyne methodology, and the function relation between the line-width triangle v of the laser and the spectrum-width triangle f of the photoelectric current heterodyne signal is obtained fitting of the three-level proportion function model. The invention presents that with the short optical fiber delay self-heterodyne method, the device can eliminate the deficiency of greatly reduced measuring precision because of not enough delayed time in the delay self-heterodyne method when the length of the delay optical fiber is less than 6 times coherence length of the laser, so as to provide an effective method of precisely measuring the line-width of the laser with narrow line-width in projects.

Description

technical field

[0001] The invention relates to a method for measuring the line width of a narrow line width laser, more particularly, it refers to a method based on the principle of the fiber delay self-heterodyne method, using a shorter fiber delay line to achieve the purpose of accurately measuring the line width , the method can effectively reduce the length of the optical fiber delay line, reduce the cost and volume, and basically do not affect the original accuracy. Background technique

[0002] Single-frequency lasers are one of the development directions of lasers in recent years. They are mainly used in many fields such as lidar, optical communication, gravitational wave measurement, high-resolution spectral measurement, and squeezed state research in quantum optics.

[0003] Ordinary light sources emit light, which is the spontaneous emission of a large number of independent oscillators. The light waves emitted by each vibrator are composed of wave trains that las...

Examples

Embodiment 1

[0059] Assuming that the linewidth of the measured laser is 10kHz, the coherence time τ c =100μs; using 2500m delay line, τ d =121.5μs, N=τ d / τ c = 0.823. Substituting the three parameters into the simulation program, the result is as follows Figure 4 As shown, it is actually the power curve when N=0.823, and the line width is 25.5kHz; " * "The line is the power spectrum curve obtained by using the uniformly widened line shape function, and the line width is 10.001kHz. The two results reflect that when the delay time of the optical fiber delay line is not large enough, the line width is 2.5 wider than the actual line width It can only roughly reflect the magnitude of the line width, and the accuracy error is too large.

[0060] According to the above method, the length of the fiber delay line is selected as 2500m, and the laser line width ranges from 2kHz to 60kHz, and 30 frequency points with a step of 2kHz are respectively selected, and the corresponding parameters ar...

technical field

[0001] The invention relates to a method for measuring the line width of a narrow line width laser, more particularly, it refers to a method based on the principle of the fiber delay self-heterodyne method, using a shorter fiber delay line to achieve the purpose of accurately measuring the line width , the method can effectively reduce the length of the optical fiber delay line, reduce the cost and volume, and basically do not affect the original accuracy. Background technique

[0002] Single-frequency lasers are one of the development directions of lasers in recent years. They are mainly used in many fields such as lidar, optical communication, gravitational wave measurement, high-resolution spectral measurement, and squeezed state research in quantum optics.

[0003] Ordinary light sources emit light, which is the spontaneous emission of a large number of independent oscillators. The light waves emitted by each vibrator are composed of wave trains that las...

Examples

Embodiment 1

[0059] Assuming that the linewidth of the measured laser is 10kHz, the coherence time τ c =100μs; using 2500m delay line, τ d =121.5μs, N=τ d / τ c = 0.823. Substituting the three parameters into the simulation program, the result is as follows Figure 4 As shown, it is actually the power curve when N=0.823, and the line width is 25.5kHz; " * "The line is the power spectrum curve obtained by using the uniformly widened line shape function, and the line width is 10.001kHz. The two results reflect that when the delay time of the optical fiber delay line is not large enough, the line width is 2.5 wider than the actual line width It can only roughly reflect the magnitude of the line width, and the accuracy error is too large.

[0060] According to the above method, the length of the fiber delay line is selected as 2500m, and the laser line width ranges from 2kHz to 60kHz, and 30 frequency points with a step of 2kHz are respectively selected, and the corresponding parameters ar...

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