| CPC G02F 1/392 (2021.01) [G01J 3/108 (2013.01); G02F 1/3503 (2021.01); G02F 1/3507 (2021.01); G02F 1/3526 (2013.01); H01S 3/094076 (2013.01); H01S 3/1106 (2013.01); H01S 3/1611 (2013.01); H01S 3/235 (2013.01); G02F 1/3551 (2013.01); G02F 2203/11 (2013.01); H01S 3/1643 (2013.01); H01S 3/1673 (2013.01); H01S 2302/00 (2013.01); H01S 2303/00 (2013.01)] | 17 Claims |
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1. A wavelength-tunable source of pulsed laser radiation for VIS-NIR spectroscopy comprising:
a pump pulse source comprising:
a laser oscillator generating a continuous train of picosecond seed pulses, defined by a first repetition rate f1 in a range from 10 kHz to 100 MHz;
a module for pulse bursts formation and amplification which provides a sequence of bursts of pump pulses, being a pump radiation,
wherein each said burst of pump pulses consists of picosecond pump pulses, repeating at a second repetition rate f2 which is higher than said first repetition rate f1 and is in a range from 200 MHz to 2 GHz; a time interval between adjacent bursts of pump pulses corresponds to a third repetition rate f3 which is lower than the second repetition rate f2 and lower than or equal to the first repetition rate f1 and is in a range from 500 Hz to 10 kHz, a duration of the adjacent bursts of pump pulses being equal to a time interval Δt and each burst of pump pulses contains from 7 to 15 consecutive pump pulses with a peak power exceeding 800 kW, while a sum energy of each burst of pump pulses is not less than 300 μJ, said module comprising:
a solid-state regenerative amplifier having one or two optical switches inside a solid-state regenerative amplifier resonator;
wherein said one or two optical switches are configured so that, by applying a voltage to one or both of said one or two optical switches, seed pulses-spaced apart by a time interval of 1 over the third repetition rate 1/f3, are trapped inside the solid-state regenerative amplifier resonator;
wherein an accuracy of a moment t0 to when the voltage is turned on ensures at least 1% energy stability of pulses output from the module for pulse bursts formation and amplification;
wherein turning off the voltage on one of said one or two optical switches or reducing the voltage on one or both of said one or two optical switches at a time moment t1, a partial transmittance of the solid-state regenerative amplifier resonator is created for the time interval Δt which is longer than a roundtrip time of said solid-state regenerative amplifier resonator, and a part of energy of a pulse circulating inside said solid-state regenerative amplifier resonator is coupled out;
wherein a bandwidth of said pump pulses, does not exceed 1 cm−1, while a duration is from 15 ps to 70 ps; and
an optical parametric oscillator comprising:
at least two mirrors forming an optical resonator of a length L2;
at least one optical parametric amplification nonlinear crystal, placed inside said optical resonator of the length L2, wherein two photons of lower energy are generated from one photon of radiation of pump wavelength λP: a signal wave photon of wavelength λS As and an idler wave photon of wavelength λI;
the pump pulse source and the optical parametric oscillator being mutually matched so that a roundtrip time of the optical resonator constituting the optical parametric oscillator is made equal to a time interval 1/f2 between adjacent pump pulses;
the optical parametric oscillator providing a sequence of bursts of output pulses, said sequence of bursts of output pulses being an output radiation of the wavelength-tunable source, wherein each said burst of output pulses consists of picosecond pulses, of a signal and/or an idler wave,
wherein for the pump wavelength λP, a phase-matching condition for optical parametric amplification in said optical parametric amplification nonlinear crystal is satisfied over an entire transparency range of the optical parametric amplification nonlinear crystal;
wherein a conversion efficiency from the sequence of bursts of pump pulses to the sequence of bursts of output pulses is at least 10% in an entire wavelength tuning range;
wherein each burst of output pulses has from 5 to 10 consecutive output pulses with a peak power exceeding 10 kW in the entire wavelength tuning range;
wherein a bandwidth of the output pulses of the output radiation does not exceed 10 cm−1;
wherein, when pumped with near-infrared laser radiation or its harmonics, the wavelength tuning range of the output radiation covers visible and near-infrared spectral regions.
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