CN106229797A - For producing the fiber optic loop time lens combination of STUD pulse - Google Patents

Abstract

A fiber ring time lens system for generating STUD pulses, using a single-mode continuous light laser as a light source, characterized in that it also includes a first photoelectric switch, an arbitrary wave generator, a second photoelectric switch, an ytterbium-doped fiber amplifier, and a band-pass filter device, a third photoelectric switch, a phase modulator and a pair of gratings; the system structure of the present invention is simple, not only a photoelectric switch can directly generate a high repetition frequency super-Gaussian pulse with a shorter pulse width, but also the optical pulse passing through the optical fiber ring The spectrum is broadened, and the laser pulse after the spectrum broadening can be compressed by a grating to generate an ultrashort laser super-Gaussian pulse (STUD pulse) with a steep rising or falling edge, and the width of the spectrum, the width of the pulse and the pulse The rising edge is arbitrarily adjustable. STUD pulses can be used to suppress parametric instability in the process of laser-driven inertial confinement fusion, and have the characteristics of novel technology and simple structure (all-fiber).

Description

Fiber-optic ring time lens system for generating STUD pulses

technical field

The invention relates to ultrashort laser pulses, in particular to a fiber ring time lens system for generating STUD pulses. The system can efficiently output adjustable, high repetition frequency STUD pulses and ultrashort pulse lasers.

Background technique

At present, parametric instability (stimulated Raman scattering, stimulated Brillouin scattering, filamentation, etc.) is one of the main reasons that ultimately limit laser-driven inertial confinement fusion. In order to suppress parametric instability, scientists from various countries have successively proposed a series of beam smoothing methods such as spectral dispersion smoothing, polarization smoothing, and continuous phase plate. Through the spatial energy distribution of the uniform beam, they allow the focal spot of the beam to move rapidly on the target surface, effectively avoiding the filamentation of the bright spot and suppressing the instability of the parameters. However, due to the higher density of the plasma interacting with the laser in the inner ring, the parametric instability generated by the laser is stronger, so it is not enough to only use the beam smoothing method.

After searching the prior art, it was found that there was an article titled "Generation of 3.5nJ femtosecond pulses from continuous-wave laser without mode locking" in Optics Letters, Volume 32, No. 11, on June 1, 2007. Generating 3.5nJ femtosecond pulses by continuous laser without mode-locking method) introduced a method based on direct phase modulation and grating compression technology to generate high repetition frequency femtosecond pulses. However, this article does not propose a method for generating ultrashort ultra-Gaussian pulses (hereinafter referred to as STUD pulses) with steep rising edges.

STUD pulses can effectively suppress the accumulation of parametric instabilities such as stimulated Raman scattering and stimulated Brillouin scattering during laser-plasma interaction. Both Q-switching and mode-locking techniques are difficult to obtain ideal STUD pulses.

Contents of the invention

The present invention aims at above-mentioned deficiencies in the prior art, provides a kind of optical fiber ring time lens system that is used to produce STUD pulse, this system can not only directly produce the high repetition frequency super-Gaussian pulse with shorter pulse width by a photoelectric switch, and can The spectrum of the light pulse passing through the fiber ring is broadened, and the laser pulse after the spectrum broadening can also be compressed by a grating to generate an ultrashort laser super-Gaussian pulse (STUD pulse) with a steep rising or falling edge, and the spectrum Width, pulse width and pulse rising edge are adjustable arbitrarily. STUD pulses can be used to suppress parametric instability in the process of laser-driven inertial confinement fusion, and have the characteristics of novel technology and simple structure (all-fiber).

The present invention is realized through the following technical solutions:

A fiber ring time lens system for generating STUD pulses, using a single-mode continuous light laser as a light source, characterized in that it also includes a first photoelectric switch, an arbitrary wave generator, a second photoelectric switch, an ytterbium-doped fiber amplifier, and a band-pass filter device, a third photoelectric switch, a phase modulator and a pair of gratings;

Along the direction of the pulsed light output by the single-mode continuous optical laser are the first photoelectric switch, the second photoelectric switch, the second photoelectric switch, the ytterbium-doped fiber amplifier, the band-pass filter, and the third photoelectric switch. The switch and the phase modulator are connected in sequence to form a fiber optic ring, and the second output direction of the third photoelectric switch is the pair of gratings;

The output terminals of the arbitrary wave generator are respectively connected with the control terminals of the first photoelectric switch, the second photoelectric switch, the third photoelectric switch and the phase modulator to provide driving signals for its work, and by outputting different signal to control the working status of each device.

The spectrum bandwidth of the single-mode continuous light laser is less than 100KHz, and the maximum output power is <100mw.

The ytterbium-doped fiber amplifier is a tuneable amplifier with an amplification range of 0-25dB and a maximum output power of 5W.

The central wavelength of the bandpass filter is 1053nm, the peak reflectivity is greater than 99%, the 3dB bandwidth is 12nm, and the sideband suppression rate is greater than 10dB.

The applicable wavelength band of the phase modulator is 1053nm, the half-wave voltage is 2.7V, the 3dB bandwidth is greater than 10GHz, and the input and output are polarization-maintaining.

The structural parameters of the two gratings of the grating pair are consistent and placed in parallel.

The system of the present invention includes three parts.

The first part uses the chopping performance of the first photoelectric switch to chop the single longitudinal mode continuous laser through the first photoelectric switch to realize the output of high repetition frequency super-Gaussian pulse. The first photoelectric switch can also modulate an optical pulse envelope of any shape.

The second part innovatively uses the time lens technology of the fiber ring, through the use of fiber amplifiers for energy compensation and band-pass filters to filter lasers and phase modulators with a center wavelength of 1053nm through the use of fiber amplifiers for the super-Gaussian pulse light cycle coupled into the fiber ring for proper phase modulation. After N-turn modulation, the spectrum of the pulsed light is broadened sufficiently, and the pulsed light becomes a chirped pulsed light, and then the super-Gaussian pulse is coupled out of the fiber ring by controlling the third photoelectric switch.

In the third part, a grating pair is creatively used to compress the output pulse, and then a high repetition rate ultra-short ultra-Gaussian pulse (STUD pulse) with a steep rising or falling edge is generated.

The shape of the pulse is generated by an arbitrary waveform generator and formed by chopping through the first photoelectric switch, so the shape and repetition frequency of the optical pulse are controllable.

The phase modulation function is added to the input optical pulse through the phase modulator in the optical fiber ring, and the input pulse is changed into a chirped pulse. By controlling the number of times the optical pulse circulates in the fiber ring, the size of the pulse chirp and the width of the pulse spectrum can be controlled. Then, the opposite chirp is compressed through the grating to realize the control of the rising or falling edge of the pulse and the pulse width. Since the phase modulation function is controllable, the above-mentioned characteristics of the pulse are controllable.

The second photoelectric switch couples the pulsed light output by the first photoelectric switch into the fiber ring, and circulates N circles along the ytterbium-doped fiber amplifier, bandpass filter, third photoelectric switch and phase modulator, and the pulsed light After the spectrum is broadened enough, the third photoelectric switch couples and compresses the pair of gratings to output an ultrashort ultra-Gaussian pulse.

Any synthesis method can be used, such as Mach-Zendt interferometer, Michelson interferometer, Fabry-Perot cavity and so on.

Compared with prior art, the beneficial effects of the present invention are:

The STUD pulse can be generated by using the system of the invention, and its pulse rising edge or falling edge, pulse width, repetition frequency, and pulse shape can be controlled arbitrarily.

Description of drawings

FIG. 1 is a schematic diagram of the optical path of Embodiment 1 of the optical fiber ring time lens system for generating STUD pulses according to the present invention.

Figure 2 is a schematic diagram of pulse spectrum broadening.

detailed description

The present invention is described in detail below in conjunction with accompanying drawing and embodiment, and present embodiment is carried out under the premise of technical scheme of the present invention, has provided detailed embodiment and specific operation process, but protection scope of the present invention is not limited to the following the described embodiment.

FIG. 1 is a schematic diagram of the optical path of Embodiment 1 of the optical fiber ring time lens system for generating STUD pulses according to the present invention. As can be seen from the figure, the fiber ring time lens system used to generate STUD pulses in the present invention adopts a single-mode continuous light laser 1 as a light source, and its composition also includes a first photoelectric switch arranged along the direction of the pulsed light output by the single-mode continuous light laser 1 After 2, through the second photoelectric switch 4, it is coupled into the fiber ring composed of the ytterbium-doped fiber amplifier 5, the bandpass filter 6, the third photoelectric switch 7 and the phase modulator 8, and the circulated laser pulse passes through the third photoelectric switch 7 is coupled out of the fiber ring, and then punched on the grating pair 9;

The second photoelectric switch couples the output pulsed light into the fiber ring, and circulates N circles along the ytterbium-doped fiber amplifier 5, filter 6, third photoelectric switch 7 and phase modulator 8 (N is an integer greater than 1), After the spectrum of the pulsed light is broadened sufficiently, it is coupled out of the fiber ring through the third photoelectric switch 7;

The output terminals of the arbitrary wave generator 3 are respectively connected with the first photoelectric switch 2 , the second photoelectric switch 4 , the third photoelectric switch 7 and the phase modulator 8 .

The spectrum bandwidth of the single-mode continuous light laser 1 is less than 10KHz, and the maximum output power is 100mw.

The ytterbium-doped fiber amplifier 5 is a tunable amplifier with an amplification range of 0-25dB and a maximum output power of 5W.

The central wavelength of the bandpass filter 6 is 1053nm, the peak reflectivity is greater than 99%, the 3dB bandwidth is 12nm, and the sideband suppression rate is greater than 10dB.

The applicable waveband of the phase modulator 8 is 1053nm, the half-wave voltage is 2.7V, the 3dB bandwidth is greater than 10GHz, and the input and output are polarization-maintaining.

The single-mode continuous optical fiber laser 1 is connected to the first photoelectric switch 2 . The continuous laser light generated by the single-mode continuous light laser is chopped by the first photoelectric switch 2 to obtain nanosecond-level super-Gaussian pulses. The super-Gaussian pulse is coupled into the optical fiber ring composed of the ytterbium-doped fiber amplifier 5, the bandpass filter 6, the third photoelectric switch 7 and the phase modulator 8 through the second photoelectric switch 4, and after N>1 cycles, the pulse The spectrum of the light is broadened sufficiently, and the chirped pulsed light is obtained by coupling out the fiber ring through the third photoelectric switch 7 . Finally, the output light with sufficient energy is dechirped through the grating pair 9, which can compress the ultra-Gaussian pulse with a rising or falling edge of 300ps and a pulse width of 2ns to a steep rising or falling edge of 4.7ps and a pulse width of 20ps ultrashort ultra-Gaussian pulses.

Wherein: the first photoelectric switch 2 receives the super-Gaussian signal generated by the Arbitrary Waveform Generator (AWG for short) 3; the phase modulator in the optical fiber ring receives the high-frequency signal with opposite phase generated by the AWG.

The single-mode continuous light laser has a spectral bandwidth of less than 100KHz and a maximum output power of 100mw.

The insertion loss of the photoelectric switch is <3dB, the switching speed is <100ps, the half-wave voltage is 2.7V, and the maximum operating frequency is 10GHz.

The ytterbium-doped fiber amplifier is a tunable amplifier with an amplification range of 0-25dB and a maximum output power of 5W.

The central wavelength of the bandpass filter 6 is 1053nm, the peak reflectivity is greater than 99%, the 3dB bandwidth is 12nm, and the sideband suppression rate is greater than 10dB.

The phase modulator 8 is applicable to a wavelength band of 1053nm, a half-wave voltage of 2.7V, a 3dB bandwidth greater than 10GHz, and input and output polarization maintaining.

The AWG has a sampling rate of 12GS/s, a bandwidth of 10GHz, 2 independent analog outputs, and 4 independent digital outputs.

The STUD pulse generated by this system plays a huge role in suppressing parameter instability in laser inertial confinement fusion.

Claims (6)

1. A fiber ring time lens system for producing STUD pulses, adopting a single-mode continuous light laser (1) as a light source, is characterized in that it also includes a first photoelectric switch (2), an arbitrary wave generator (3), a second Photoelectric switch (4), ytterbium-doped fiber amplifier (5), bandpass filter (6), third photoelectric switch (7), phase modulator (8) and grating pair (9); Along the pulses output by the single-mode continuous optical laser (1), the light direction is successively the first photoelectric switch (2), the second photoelectric switch (4), the second photoelectric switch (4), Ytterbium-doped optical fiber amplifier (5), band-pass filter (6), the third photoelectric switch (7) and phase modulator (8) are connected successively to form an optical fiber ring, in the second of the third photoelectric switch (7) The output direction is the grating pair (9); The output terminals of the arbitrary wave generator (3) are respectively connected with the control of the first photoelectric switch (2), the second photoelectric switch (4), the third photoelectric switch (7) and the phase modulator (8) The terminals are connected to provide drive signals, and control the working status of each device by outputting different signals. 2. The fiber ring time lens system for producing STUD pulses according to claim 1, characterized in that the spectral bandwidth of the single-mode continuous light laser (1) is less than 100KHz, and the maximum output power is less than 100mw. 3. the optical fiber ring time lens system for producing STUD pulse according to claim 1, it is characterized in that described ytterbium-doped fiber amplifier (5) is a tunable amplifier, the amplification range is 0～25dB, and the maximum output power is 5W. 4. the optical fiber ring time lens system for producing STUD pulse according to claim 1, it is characterized in that the center wavelength of described band-pass filter (6) is 1053nm, peak reflectivity is greater than 99%, and 3dB bandwidth is 12nm, the sideband suppression rate is greater than 10dB. 5. the optical fiber ring time lens system for producing STUD pulse according to claim 1, it is characterized in that the applicable wave band of described phase modulator (8) is 1053nm, half-wave voltage 2.7V, 3dB bandwidth is greater than 10GHz, Input and output are polarized. 6. The optical fiber ring time lens system for generating STUD pulses according to any one of claims 1 to 5, characterized in that the pair of gratings (9) are placed in parallel, and the structural parameters of the two gratings are consistent.