Injected laser and method for generating longitudinal multimode laser pulses

A method for generating multi-longitudinal mode laser pulses comprising the following steps:

• emission of a monochromatic continuous laser radiation by a fibred laser diode emitting a monochromatic continuous laser radiation at a wavelength (λc) of 1064 nm,
• periodic modulation, as a function of time, at a modulation frequency (fm), of a phase of the monochromatic continuous laser radiation using an optical modulator with a waveguide integrated on a lithium niobate substrate so as to generate a polychromatic injection radiation having a plurality of discrete wavelengths,
• injection of the polychromatic injection radiation in a triggered laser cavity comprising a Q-switched triggering device and an optical amplifying medium arranged inside the laser cavity, the optical amplifying medium being a neodymium-YAG crystal, the optical amplifying medium having a spectral amplification band, and the laser cavity having a free spectral band (FSR) lower than the spectral bandwidth of the optical amplifying medium, the modulation frequency (fm) being equal to a natural integer multiple of the free spectral band (FSR) of the laser cavity, so that the plurality of discrete wavelengths of the polychromatic injection radiation is tuned over a plurality of longitudinal resonance modes of the laser cavity located inside the gain band of the optical amplifier,
• amplification of the polychromatic injection radiation in the triggered laser cavity, and
• triggering of the emission of a multi-longitudinal mode laser pulse.

An injected laser comprising:

• an optical amplifying medium arranged inside a triggered laser cavity, the optical amplifying medium having a spectral amplification band,
• the laser cavity having a free spectral range (FSR) lower than the spectral bandwidth of the optical amplifying medium, the laser cavity determining longitudinal resonating modes spectrally separated by the free spectral range (FSR),
• wherein:
• the injected laser comprises a single injection source adapted to emit a monochromatic continuous laser radiation,
• the injected laser comprises an optical phase-modulation device arranged between the injection source and the laser cavity, the optical phase-modulation device being configured to periodically modulate as a function of time a phase of the monochromatic continuous laser radiation at a modulation frequency (fm) equal to a natural integer multiple of the free spectral range (FSR) of the laser cavity, so that the phase-modulated injection source generates a polychromatic injection radiation having a plurality of discrete wavelengths located inside the gain band of the optical amplifier, the plurality of discrete wavelengths being tuned to a plurality of longitudinal resonance modes of the laser cavity,
• the laser cavity and the optical amplifier medium being adapted to receive said polychromatic injection radiation and to generate a multi-longitudinal mode laser pulse, and
• the optical phase-modulation device being configured to sinusoidally modulate the phase of the monochromatic continuous laser radiation as a function of time with a modulation depth m, so that the polychromatic injection radiation comprises about 2m+1 discrete wavelengths, and
• the modulation depth m is equal to about 1.4 radians so that the polychromatic injection radiation comprises three discrete wavelengths.