Compact 589 nm yellow source generated by frequency‐doubling of passively Q‐switched Nd:YVO₄ Raman laser

Abstract

Compact 589 nm yellow source was reported and generated from intracavity frequency-doubling of c-cut YVO 4 / Nd:YVO 4 /YVO 4 Raman laser. A Cr 4+ :YAG/YAG composite was adopted for compact passively Q-switching operation. Double-end composited Nd:YVO 4 crystal was designed to reduce the thermal effect and increase Raman crystal length. Both noncritical phase-matching (NCPM) LBO crystal and critical phase-matching (CPM) BBO crystal were used as frequency doubling crystal for comparison. 780 mW output power of 589 nm yellow emission was achieved with an incident pump power of 16 W. The pulse repetition frequency and pulse width were 41 kHz and 3.6 ns at the maximum output power, respectively. The results show passively Q-switched operation provides a compact method to obtain 589 nm yellow emission.

A Brief Review on Nonlinear Photonic Crystals Induced by Direct Femtosecond Laser Writing

“…The SH intensity is much lower in the engineered area than that in the nonengineered area, which proves the reduction in χ (2) due to laser inscription. The average minimal SH intensity is 0.225, which indicates that χ (2) can be further reduced. Reprinted with permission from Ref.…”

A Brief Review on Nonlinear Photonic Crystals Induced by Direct Femtosecond Laser Writing

“…Frequency conversion processes are employed for the generation of new, desired frequencies, which has attracted many research interests due to its existing and potential applications in nonlinear photonics, including new laser sources [1,2], nonlinear optical microscopies [3,4], optical communications [5,6], nonlinear holograms [7], optical tweezers [8][9][10], and quantum information [11,12]. Several processes are available to obtain nonlinear frequency conversion, including second harmonic generation (SHG), differencefrequency generation (DFG), sum-frequency generation (SFG), optical parametric oscillation (OPO), and optical parametric amplification (OPA) [13].…”

“…Additionally, the conversion efficiency of BPM is highly limited by walk-off angle [13]. The other way is to periodically pole second-order nonlinearity (χ (2) ) to obtain a quasiphase matching (QPM) [14][15][16]. Via QPM, not only can the largest nonlinear coefficient be utilized, but also can the spatial walk-off angle be avoided.…”

“…Via QPM, not only can the largest nonlinear coefficient be utilized, but also can the spatial walk-off angle be avoided. As long as χ (2) is spatially modulated, a reciprocal vector lattice (RVL) G m is produced, which contributes to interacting wave vectors [17]. Consequently, the quasiphase matching condition is k F − 2 k SHG − G m = 0.…”

“…For example, a simple 1D grating (Figure 1a) gives G m = 2mπ Λ , where m is an integer, and Λ = 2l C is the poling period. According to the Fourier transform, the intensity of the corresponding RVL is 2 mπ when the duty cycle is 0.5. The first-order RVL with m = 1 has the largest Fourier coefficient 2 π .…”