Ultrafast pulse laser system utilizing intensity pulse shape correction

Patent metadata

Field	Value
Publication number	US-11095089-B2
Application number	US-201716088121-A
Country	US
Kind code	B2
Filing date	Mar 29, 2017
Priority date	Mar 31, 2016
Publication date	Aug 17, 2021
Grant date	Aug 17, 2021

Abstract

The ultrafast pulse fiber laser system is configured with scalable output power and operative to reduce degradation of pulse integrity. The disclosed laser system is configured to suppress the pulse distortion through improvement of initial pulse contrast between main and side pulses and improved pulse shape using chirped pulse amplification and a fast intensity modulator driver by a corrected electrical signal that is generated from the original optical signal. The structure providing the improvement includes the photodiode, which is operative to measure the chirped optical pulse and convert it to the electrical signal, and analog electronics that quickly converts the electrical signal to the required signal that suppress the side pulses.

First claim

The invention claimed is:

1. A sub-nanosecond (sub-ns) pulsed laser system for outputting near transform limited pulses, comprising:
a beam splitter receiving a train of chirped pulses of light signal in a ps-ns pulse duration range and operative to divide each light signal into first and second portions;
at least one optoelectronic converter receiving and converting the second portion of the light signal into a first radio-frequency (RF) signal;
an intensity modulator receiving the first portion of each light signal; and
at least one tunable radio-frequency (RF) generator scheme receiving and processing the first RF signal applied to the intensity modulator so as to correct spectral intensity profile of the chirped pulse at an output of the intensity modulator.

2. The sub-ns pulsed laser system of claim 1 further comprising
a single transverse mode (SM) seed laser configured as a gain-switched or mode locked laser which outputs the train of chirped sub-ns pulses of light signal;
a pulse stretcher located between the SM seed laser and beam splitter and configured to chirp sub-ns pulses to the ps-ns pulse duration range;
a single or multiple amplifying stages each provided with a fiber amplifier which receives and amplifies the first portion of light signal with the corrected spectral intensity profile;
a pulse compressor receiving the amplified first portion of light signal of each pulse with the corrected spectral profile and operative to output the train of sub-ns pulse,
wherein the chirped pulses each acquire an improved pulse contrast in time domain and spectral ripples in frequency domain at an input of the beam splitter.

3. The sub-ns pulsed laser system of claim 2 further comprising at least one fiber delay component guiding the second portion of light signal between the beam-splitter and optoelectronic converter to synchronize the amplified RF signal and the first portion of light signal which is coupled into the intensity modulator.

4. The sub-ns pulsed laser system of claim 3 , wherein the time delay component includes a multi part spool with a fiber wrapped around multiple parts which are controllably displaceable relative to one another.

5. The sub-ns pulsed laser system of claim 1 , wherein the beam splitter includes a fiber coupler configured to divide each light signal so that the first portion of light signal, coupled to the intensity modulator, is greater than or smaller than or equal to the second portion of the light signal guided to the optoelectronic converter, the one optoelectronic converter being a fast photodetector operating in a bandwidth of up to several hundred gigahertz (GHz) and converting the received second portion of light signal of each chirped pulse into the one RF signal which is proportional to an optical intensity of light in each chirped pulse.

6. The sub-ns pulsed laser system of claim 1 , wherein the one tunable RF generator scheme is configured with;
an RF filter coupled to an output of the one optoelectronic converter and operative to pass a predetermined region of the first RF signal,
an RF inverter flip-flopping the filtered region of the first RF signal, and
an RF amplifier operative to amplify the flip-flopped filtered region of the first RF signal applied to the intensity modulator to correct the spectral intensity profile of the first portion of light signal.

7. The sub-ns pulsed laser system of claim 1 , wherein the intensity modulator is a Mach-Zehnder interferometer provided with first and second waveguide arms which guide respective replicas of the first portion of light signal, at least first arm including a phase modulator which receives the amplified first RF signal inducing a phase shift on the replica of the first portion of light signal guided in the first arm, the first and second replicas being interposed at an output of the Mach-Zehnder interferometer so as to convert a phase difference between the first and second replicas to the correct intensity profile of the first portion of light signal in each chirped pulse.

8. The sub-ns pulsed laser system of claim 1 further comprising:
a second RF generator scheme configured identically to the one RF generator scheme and receiving a fraction of the second portion of the light signal to generate a second RF signal,
the intensity modulator being the Mach-Zehnder interferometer provided with first and second waveguide arms which guide respective replicas of the first portion of light signal, the first and second arms including respective one and second phase modulators which receive amplified first and second RF signals with different amplitudes from respective one and second RF generator schemes, the one and second RF signals inducing a phase shift on both replicas of the first portion of light signal which interfere at an output of the Mach-Zehnder interferometer so as to convert a phase difference between the first and second replicas to the correct intensity profile of the first portion of light signal in each chirped pulse.

9. The sub-ns pulsed laser system of claim 1 further comprising
a second RF generator scheme operative to generate a second RF signal;
a second tunable RF amplifier operative to amplify the second RF signal having an amplitude different from the RF signal generated by the one RF generator scheme, the intensity modulator being a Mach-Zehnder interferometer provided with first and second waveguide arms which guide respective replicas of the first portion of light signal, the first and second arms including respective one and second phase modulators which receive respective amplified RF signals, the first and second RF signals inducing respective phase shifts on the first and second replicas of the first portion of light signal which are interposed at an output of the Mach-Zehnder interferometer so as to convert a phase difference between the first and second replicas to the correct intensity profile of the first portion of light signal in each chirped pulse.

10. The sub-ns pulsed laser system of claim 9 further comprising
a first fiber delay component between the beam splitter and one optoelectronic component;
an additional fiber coupler located between the first fiber delay component and one optoelectronic converter and operative to split the second portion of the light signal into first and second fractions,
an additional fiber delay component between the additional coupler and the second RF signal generator schemes, wherein the first and second fiber delay components are configured to provide respective fractions of the second portion of light signal with such a time delay that the first and second RF signals are applied across respective phase modulators synchronously with respective replicas of the first portion of light signal, wherein the additional time delay component includes a multi part spool with a fiber wrapped around multiple parts which are controllably displaceable relative to one another.

11. The sub-ns pulsed laser system of claim 1 , wherein the intensity modulator is a semiconductor optical amplifier receiving the first RF signal to selectively provide gain to the first portion of light signal so as to obtain the correct intensity profile at an output of the semiconductor optical amplifier.

12. The sub-ns pulsed laser system of claim 1 , wherein the RF generator scheme operates at
a relatively high frequency ranging between 5 and 500 GHz to correct intensity ripples in the first portion of signal light at the output of the intensity modulator, or
at a relatively low frequency of up to 2 GHz to provide each pulse of the modulated first portion of signal light with a parabolic shape in temporal and spectral domain

Assignees

• Ipg Photonics Corp

Inventors

• Yusim Alex
• Samartsev Igor
• Shkurihkin Oleg

Classifications

• H01S3/10015

  by monitoring or controlling, e.g. attenuating, the input signal · CPC title

• H01S3/0085

  Modulating the output, i.e. the laser beam is modulated outside the laser cavity · CPC title

• H01S3/1003 Primary

  tunable optical elements, e.g. acousto-optic filters, tunable gratings · CPC title

• H01S3/0057

  Temporal shaping, e.g. pulse compression, frequency chirping (soliton generation and propagation G02F1/3513, H01S3/063 and H01S3/108) · CPC title

• H01S3/1305 Primary

  Feedback control systems · CPC title