Abstract
White laser with balanced performance of broad bandwidth, high average and peak power, large pulse energy, high spatial and temporal coherence, controllable spectrum profile, and overall chroma are highly desirable in various fields of modern science. Here, for the first time, we report an innovative scheme of harnessing the synergic action of both the second-order nonlinearity (2nd-NL) and the third-order nonlinearity (3rd-NL) in a single chirped periodically poled lithium niobate (CPPLN) nonlinear photonic crystal driven by a high-peak-power near-infrared (NIR) (central wavelength~1400 nm, energy~100 μJ per pulse) femtosecond pump laser to produce visible to near infrared (vis-NIR, 400-900 nm) supercontinuum white laser. The CPPLN involves a series of reciprocal-lattice bands that can be exploited to support quasiphase matching for simultaneous broadband second- and third-harmonic generations (SHG and THG) with considerable conversion efficiency. Due to the remarkable 3rd-NL which is due to the high energy density of the pump, SHG and THG laser pulses will induce significant spectral broadening in them and eventually generate bright vis-NIR white laser with high conversion efficiency up to 30%. Moreover, the spectral profile and overall chroma of output white laser can be widely modulated by adjusting the pump laser intensity, wavelength, and polarization. Our work indicates that one can deeply engineer the synergic and collective action of 2nd-NL and 3rd-NL in nonlinear crystals to accomplish high peak power, ultrabroadband vis-NIR white laser and hopefully realize the even greater but much more challenging dream of ultraviolet-visible-infrared full-spectrum laser.
Highlights
In the past 60 years, the collective action of laser technology and nonlinear optics has continuously pushed the realm of lasers into an ever-increasing height and ever-expanding frontiers in terms of laser materials, pulse duration, spectral width, power, and energy
The properties of white laser, including the intensity, spectra, and chroma, can be modulated in a broad range. This capability of chirped periodically poled lithium niobate (CPPLN) can be attributed to the synergic action of 2nd-NL and 3rd-NL that is enabled by the special quasiphase matching (QPM) properties of CPPLN in combination with the high peak power and broad bandwidth nature of a pump femtosecond pulse laser
The 3rdNL enabled by the peak power of pump laser will account for the initial spectral broadening effect, and new spectral components add into the pump laser pulse when it transports in CPPLN
Summary
In the past 60 years, the collective action of laser technology and nonlinear optics has continuously pushed the realm of lasers into an ever-increasing height and ever-expanding frontiers in terms of laser materials (gas, liquid, solid, semiconductor, and fiber), pulse duration (continuous wave, nanosecond, picosecond, femtosecond, and attosecond), spectral width, power, and energy. A laser machine, with deliberate infrastructure design of cavity, gain medium, and pump source, outputs one or several specific discrete wavelengths of continuous-wave coherent light or a series of phase-fixed optical pulses with high coherence but only covering a limited spectral bandwidth. When inputting these lasers into a nonlinear crystal or material, nonlinear optical interaction will convert part of the energy into new lasers of different discrete wavelengths or spectral bands. It remains a grand challenge to construct an all-spectrum laser machine that outputs a laser beam covering an extremely broad spectral bandwidth comparable with our everyday sunlight, which ranges from ultraviolet to midinfrared (300-5000 nm), while at the same time exhibiting high spatial and temporal coherence (i.e., beam collimation and pulse compression capability far exceeding the incoherent solar blackbody radiation) as well as high power and energy
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