1981年，第一台飞秒激光器研制成功，具有较短脉冲持续时间和较高峰值功率的飞秒脉冲，为光与物质相互作用的研究提供了重要基础，随后基于超快飞秒脉冲激光的各种研究方法被应用在物理，化学，生物和材料科学研究等领域。受激光增益介质的发射谱线限制，导致固体激光器的输出波长一般被限制在几个离散区域，或者只能在某一小范围内调谐，且发射波长多分布在近红外光谱范围。而在不同研究领域的应用中，研究人员往往需要大范围内可调谐的激光波长。因此对现有激光波长进行频率变换以产生可调谐的不同波长的飞秒脉冲显得尤为重要。多色可调谐宽带脉冲的产生目前主要基于如下两种过程，参量放大过程和四波混频过程。不同于参量放大过程，四波混频过程产生的多色飞秒脉冲具有同时产生多色角分散的波长可调谐飞秒脉冲，并且可以利用的非线性介质更为广泛。但无论是基于四波混频过程还是参量放大过程，为了产生可调谐多色飞秒脉冲，都必须首先产生一束宽带的超连续白光，而超连续白光的光谱宽度则决定了最后产生的多色脉冲的波长范围，另外，超连续白光的稳定性对于最终多色脉冲的稳定性也有着至关重要的影响。最近研究人员开展了基于多片固体介质组成的薄片组产生超连续白光的研究，相较于在常规厚蓝宝石介质，此方式产生的超连续白光具有更好的稳定性及更宽的光谱和更好的光束质量。其次，无论基于四波混频过程还是参量放大过程产生多色飞秒脉冲，除了需要宽带超连续白光以外，非线性介质也扮演着重要的角色，非线性介质是发生频率转换的根本前提。现有的非线性晶体相位匹配范围主要在可见波段、近红外和紫外波段。对于深紫外倍频波段，目前主要依靠价格昂贵的光子晶体来实现频率转换。而价格低廉的常规非线性晶体的研究还非常少，因此对于深紫外倍频晶体非常值得进行探索研究。基于以上分析，本文研究主要内容及得到部分结果如下：

1，基于Yb：KGW高重复频率飞秒激光器搭建四波混频实验装置。中心波长为1028 nm，脉宽为290 fs的脉冲激光作为基频光部分经过常规厚蓝宝石介质产生近红外超连续光，与另一部分基频光在BBO晶体上发生四波混频过程。得到波长为1030 nm左右的一阶频率转换光谱。

2，设计生长非Π共轭体系下的深紫外倍频晶体NNPF（NaNH₄PO₃F·H₂O），经计算发现非线性晶体NNPF最低相位匹配波长为194 nm，且通过倍频实验验证了非线性晶体NNPF在515 nm到315 nm的倍频信号的产生。

3，对于基于多片固体介质组成的薄片组的脉冲展宽进行了文献调研，发现固体薄片组产生的超连续光相较于常规厚非线性介质中产生的超连续光更加稳定，并且可以获得更宽的带宽、更高的能量和更好的光束质量。因此可以替代OPA及四波混频装置中常规厚介质中产生的超连续光。实验中将中心波长为800 nm基频光通过四片0.1 mm厚度的熔融石英后观察光谱展宽结果。

In 1981, successfully developed the first femtosecond laser, with short pulse duration and high peak power, provides an important basis to the research of light and matter, on the basis of ultrafast femtosecond pulse laser research methods are used in physics, chemistry, biology and materials science research and other research field. Output wavelength of laser are limited by laser gain medium, generally in a few discrete areas, which distribution in the near infrared spectral range, or can only be tuned in a small scope. However, in different research applications, researchers often need to tunable wavelengths over a wide range，that can not be directly generated by lasers. Therefore, it is particularly important to perform frequency conversion on lasers to generate tunable femtosecond laser pulses. There are two main ways to generate tunable multicolored femtosecond laser pulses, one is based on optical parametric amplification, the other is based on four-wave mixing. Compared with optical parametric amplification system, the four-wave mixing technique has several advantages for obtaining tunable femtosecond pulses. A number of up and down-shifted multicolor femtosecond pulses can be simultaneously obtained and spatially separated from the input beams. And second using of four-wave mixing interactions in transparent solid-state media, corresponding to a purely third-order nonlinear optical susceptibility, that have more open choice than optical parametric amplification system. But both based on four-wave mixing process and parametric amplification process produces tunable multicolor femtosecond pulse, a broadband spectrum is necessary, the spectral width of supercontinuum determines the range of the sideband signal, the stability of the supercontinuum for signal stability also has a direct impact. Recent studies have found that the supercontinuum white light generated by using multi-plate medium replace the traditional ones has better stability, wider spectrum and better beam quality. On the other hand, the nonlinear medium is the fundamental for frequency conversion, whether the multi-color femtosecond pulse is generated by the four-wave mixing technique or the parametric amplification process. The range of phase matching for existing nonlinear crystal is mainly in the visible, near infrared and ultraviolet, and very seldom nonlinear crystals above 5 um and below 200 nm. To date, only KBBF directly generate laser shorter than 200nm by second harmonic generation. However, its high toxic beryllium element component and high tendency of layered crystal growth limit its applications greatly. And the study of deep ultraviolet crystals is necessary to extend the wavelength to ultraviolet. Based on the above analysis, the main contents and some results of this thesis are as follows:

1, We demonstrate the simultaneous generation of multicolor femtosecond laser pulses in a 0.5 mm Type I BBO crystal from 1028 nm fundamental and weak near-IR supercontinuum. And we found that the sideband signal is around 1030 nm with about 15nm width.

2, We discover the best alignment of non-π-conjugated species that selectively enhances the DUV nonlinearity. According to the calculated refractive index dispersion curve, the shortest SHG wavelength is estimated to be 194 nm. The direct frequency doubling conversion at 515, 400, 335, 315 and 300 nm was detected on a setup using a Yb:KGW femtosecond laser.

3, A literature survey on pulse broadening based on multi-plate is conducted, and it is found that the supercontinuum light generated by multi-plate is more stable and with great beam quality than that generated in thick medium, and also can achieve wider spectral width and higher energy. We demonstrate spectral broadening in solid-state materials, by focusing the 800-nm pulses into 4 thin fused silica plates.