| The phase of the carrier frequency with respect to the pulse envelope in few-cycle laser pulses, which can be described by the concept of carrier-envelope phase (CEP) plays a crucial role in many nonlinear experiments correlated with electric field intensity, such as attosecond science and optical frequency metrology. As attosecond laser pulses become more and more narrow and its challenging applications, controlling and measuring the CEP of femtosecond laser pulses have now turn to one of the most fascinated research.The main purpose of this work is to explore novel schemes and techniques for stabilizing the CEP of ultrashort laser pulses. And the experimental work is concentrated on building up a CEP-stabilized intense few-cycle laser system.In order to stabilize the CEP of ultrashort laser pulses, we have proposed several innovative setups. The first one is based on cascaded optical parametric amplifier (OPA). The combination of different type OPAs not only realize the output of intense, broadband spectrum, CEP-stabilized ultrashort laser pulses, but also avoid the detrimental effects on the CEP of signal pulses in white-light seeded OPA. It is one of the effective methods for stabilizing the CEP of ultrashort laser pulses.We have observed for the first time colored conical emission due to the spatiotemporal modulational instability in second harmonic generation of ultrashort laser puses. As a consequence, the strong nonlinearity between fundamental waves and second harmonic has balanced their group velocity dispersion and diffraction, which lead to the great improvement of energy conversion. Therefore, we have proposed stabilizing the CEP of ultrashort pulses by use of modulational instability assisted OPA. This method take full advantage of modulational instability assisted OPA, facilitating the generation of widely tunable, CEP-stabilized intense ultrashort pulses.And we also proposed CEP self-stabilization by use of difference frequency generation between mudulational up-conversion amplification and pump pulses. Due to the white-light seeded amplification of colored conical emission, mudulational up-conversion amplification has very good beam quality and broadband spectrum with the same CEP as pump pulses. By tuning the central wavelength of mudulational up-conversion amplification, widely tunable of the CEP-stabilized difference frequency signal is realized.When stepping toward the goal of building up a CEP-stabilized intense few-cycle laser system, we have developed many key techniques for it.We have proposed a novel scheme for building CEP-stabilized intense few-cycle laser system by use of all-optical CEP-stabilizer and optical parametric chirped pulse amplifier (OPCPA). All-optical CEP-stabilizer achieved absolute stabilize of CEP of ultrasgort pulses. OPCPA can not only boost the energy of laser pulses, but also preserve its CEP in the whole process. It is one of the most effective methods for uilding CEP-stabilized intense few-cycle laser system.And we have also proposed generation of accurate synchronized pump pulses for OPCPA operated on 800 nm Ti:sapphire lasers by use of continues-wave (CW) seeded NOPA. The continues-wave provides sufficient photons in the parametric interaction time, which greatly restrain the fluorescence amplification. Due to the good beam quality of the CW laser beam, the output signal exhibits large single pulse energy and good beam quality. We have developed 1064 nm CW laser, 632.8 nm laser and intracavity of He-Ne laser as the seed pulse for NOPA, respectively. These scheme can generate accurate synchronized pump pulses with 800 nm Ti:sapphire lasers. The time jitter of the generated pump pulse with respect to the 800 nm pulse was measured about 10 fs in a few seconds. The generated background-free 1064 nm pulse can be further amplificted and the frequency doubled to produce an accurately synchronized pump source for OPCPA for the same Ti:sapphire laser.
|
PDF Full Text Request