Laser device for generating an optical frequency comb
The invention relates to a laser device comprising a laser source ( 1 ), which is configured to emit pulsed laser radiation ( 2 ) with a spectrum in the form of a frequency comb having a plurality of equidistant spectral lines, an optical modulator ( 3 ), which is configured to shift the frequency of the laser radiation ( 2 ), and a control unit ( 10 ), which is configured to control the modulator ( 3 ) by means of a control signal ( 6 ). It is the object of the present invention to demonstrate an improved way, compared to the prior art, of generating an optical frequency comb that is stabilized in terms of the CEO frequency, in which the CE phase is also adjustable. To this end, the invention proposes that the laser radiation ( 2 ) emitted by the laser source ( 1 ) is stabilized in terms of the carrier-envelope frequency. Furthermore, the invention relates to a method of generating an optical frequency comb.
1. A laser device comprising:
a laser source, which is configured to emit pulsed laser radiation with a spectrum in the form of a frequency comb having a plurality of equidistant spectral lines, which laser radiation emitted by the laser source is stabilized in terms of a carrier envelope frequency,
an optical modulator, which is configured to shift at least one of a phase of the pulsed laser radiation and a frequency of the pulsed laser radiation, and
a control unit, which is configured to control the optical modulator by means of a control signal, wherein the control unit is further configured to set a phase of the control signal and thus to adjust a carrier envelope phase of the pulsed laser radiation to a pre-determinable value, and wherein the control unit is further configured to increment the phase of the control signal by a predefined value from laser pulse to laser pulse to set the carrier envelope frequency of the laser radiation.
2. The laser device according to claim 1 , wherein the pulsed laser radiation emitted by the laser source is also stabilized in terms of a pulse repetition frequency.
3. The device according to claim 1 , wherein the optical modulator is an acousto-optic modulator, wherein the control signal excites an acoustic wave in the medium of the acousto-optic modulator.
4. The device according to claim 3 , wherein the control unit is configured to generate the control signal as a radio-frequency signal at the pulse repetition frequency of the pulsed laser radiation or an integer multiple thereof.
5. The device according to claim 3 , wherein the control unit is configured to generate the control signal as a radio-frequency signal at a carrier envelope frequency shifted by a pre-definable frequency offset relative to a pulse repetition frequency of the pulsed laser radiation or an integer multiple thereof.
6. The device according to claim 1 , wherein the carrier envelope frequency of the pulsed laser radiation emitted by the laser source equals zero.
7. The device according to claim 1 , wherein the laser source further comprises:
a mode-locked oscillator,
two separate radiation paths for the pulsed laser radiation emitted by the mode-locked oscillator, wherein the optical modulator is located in one of the two radiation paths, and
a difference-frequency generator, in which the pulsed laser radiation supplied via the two radiation paths is superposed.
8. A method of generating an optical frequency comb, comprising the steps of:
generating pulsed laser radiation with a spectrum in the form of a frequency comb having a plurality of equidistant spectral lines, which laser radiation is stabilized in terms of a carrier envelope frequency, and
shifting a phase and/or a frequency of the pulsed laser radiation according to a control signal,
wherein the carrier envelope frequency of the pulsed laser radiation is set by means of an acousto-optical modulator, by phase adjustment of the control signal including incrementing the phase of the control signal by a predefined value from laser pulse to laser pulse.
9. The method according to claim 8 , wherein the carrier envelope frequency of the pulsed laser radiation is shifted by a pulse repetition frequency or an integer multiple thereof.
10. The method according to claim 8 , wherein the carrier envelope frequency of the pulsed laser radiation is shifted by a frequency that differs from a pulse repetition frequency or an integer multiple thereof by a frequency offset.