The Ultra-broadband Mid-infrared Optical Parametric Amplification Technology And Its Application

The “bottleneck” problem of the gain-bandwidth is more serious, and limits thebandwidth, conversion efficiency, and tunability of the optical parametric progress,since the three wavelengths in the mid-infrared optical parametric generation andamplification exist in two intervals of the crystal normal dispersion and anomalousdispersion. This thesis is in close connection with the Major Program of NationalNatural Science Foundation of China “On the basis of the key science and technologyissues of high peak power, tunable infrared laser technology”, and focusing on thefollowing of the work, and has made some innovative results:1. To precisely synchronize the seed pulse and pump pulse of the mid-infraredoptical parametric amplifier, based on the electronic phase lock loop (PLL) and globalsynchronous clock technique, a modified active synchronous technique has beenproposed and used for the synchronization between femtosecond (fs) and picoseconds(ps) laser regenerative amplifiers with different wavelengths based on independentseed oscillators and pump lasers. As the outputs of the pump lasers and the operationsof the regenerative amplifiers were synchronized to the global synchronous clockgenerated by the precisely synchronized seed oscillators, the impact of the time errorof the three delay generators has been minimized, and the clock jitter of the fs pumplaser has been avoided, the two systems have been precisely synchronized and ranstably without readjusting. The high-precision fs and ps laser synchronization, notonly laid an experimental foundation for the mid-infrared optical parametricamplification, also widely used in various pumped-probe detection experimentsbased on the synchronization technology of laser;2. A modified statistical method based on the error propagation relation betweenthe independent variables and the conventional optical cross-correlation technique hasbeen proposed and using for the accurate measuring the root-mean-square relativetiming jitter of the two regenerative amplifiers. The measuring results show theroot-mean-square relative timing jitter is0.66ps, which is the highest level of thereported synchronization systems. This new synchronization laser relative time jittermeasurement techniques, has solved the high precision, highly credible measurementof the relative time jitter of the low repetition rate femtosecond and picosecondsynchronization pulses, and can be widely used in a variety of synchronized laser systems for the relative time jitter measurement;3. To overcome the gain-bandwidth "bottleneck" problem of the mid-infraredoptical parametric amplification, based on fan-out periodically poled crystal andspatial dispersion technique, a new scheme for ultra-broadband optical parametricchirped-pulse amplification is proposed and investigated. This scheme has made fulluse of the full two-dimensional characteristics of the quasi phase-matched fan-outperiodically poled crystal, added the use of another space dimension, so that obtai ns anewfound freedom degree for the bandwidth expansion, spectrum and waveformreshaping. Theoretically, gain-bandwidth can be expended by simply adding thehorizontal width of the crystal, while maintaining the crystal length, thus the"bottleneck" of the balance between the bandwidth and gain in current opticalparametric amplifier has been broken. In addition, it is easy to combine with theoptical spatial phase modulator, spatial amplitude modulator, and gain adjustment toreshape the spectral characteristics and the waveform of the second-frequency wave.Because this scheme makes extensive use of the horizontal space of the crystal, isespecially suitable for high-power and even ultra-high-power optical parametricamplification and nonlinear frequency transforming;4. Combination of multi-pumping source technology, the gain-bandwidth andspectral characteristics of3300nm infrared chirped pulse optical parametric amplifierwith different crystal structures and different pumping conditions has beencomparatively investigated, and numerical calculation results show that, the-3dBgain bandwidth of mid-infrared optical parametric chirped pulse amplifier using afan-out periodically poled5%MgO-doped congruent lithium niobate with aconfiguration of50.55mm3and two pump beams, exceeds320nm and can befurther broadened, In addition, we can also control the gain of the particular channelsor regions, and, therefore, the gain of the spectrum centered at these channels orregions by separately adjusting their intensity and position, and compensate forfrequencies at the spectrum wings by adding a pump pulse in the correspondingspatial regions. This new broadband parametric amplification structure can be widelyused for sum frequency generation, difference frequency generation and othernonlinear optical parametric process;5. Based on the optical structure of the new ultra-broadband optical parametricamplification, a new ultra-wideband second-harmonic generation system has beenproposed and studied, which overcomes the shortcomings of current second harmonicconversion programs, not only has a wider conversion bandwidth and higher efficiency, but also adjustment convenience and crystal flexibility. Because easilydesign features of the quasi-phase matching crystal structure by use of lithographymanufacturing process, an improved second harmonic generator, with flat-toppedspectrum and ultra-broadband output with flat conversion efficiency, has been studied,the results show that the new second-harmonic generation cannot only greatly expandthe conversion bandwidth, but also achieve capability for almost any output spectralshaping, which is expected to develop into a new broadband second harmonicconversion solution.