Optical vortex pumped mid-infrared optical parametric oscillator

Abstract

The first demonstration of a mid-infrared optical parametric oscillator pumped by 1-μm optical vortex pulses is presented. A 0.5-mJ 2-μm fractional vortex pulse having half-integer topological charge is generated. Using this system, 0.24-mJ vortex pulses with a topological charge of 1 can be created. The topological charges of the mid-infrared vortex pulses are observed by an interferometric technique in combination with second-harmonic frequency conversion.

Controlled switching of orbital angular momentum in an optical parametric oscillator

“…Since the beams with non-integer multiples of OAM per photon have neither circular symmetry nor propagate in a structurally stable fashion [32], unlike Ref. [24], we do not observe any fractional vortex beam from the DRO. However, when the DRO is operated near degeneracy, with identical signal and idler losses [see mirror transmission in Fig.…”

“…However, it is interesting to note that the OAM of the pump is only transferred to the signal and not to the idler radiation, resulting in an output OAM state, jl s ; l i i j1; 0i, although both j1; 0i and j0; 1i are equally probable output states of the OPO. Unlike previous reports [23][24][25], the use of QPM Research Article crystal here eliminates the role of anisotropy due to birefringence in transferring OAM to the signal radiation.…”

“…Therefore, direct generation and control of OAM modes in an OPO can offer an intriguing route to provide high-power OAM beams at arbitrary wavelengths. Previous efforts [22][23][24][25] have confirmed the possibility of generating OAM beams from OPOs, where it was shown that the transfer of OAM from the pump to the output beams was dictated by cavity detuning and anisotropic cavity mode propagation due to crystal birefringence [25]. Therefore, without active control, the transfer of OAM from the pump is constrained to only one of the output beams.…”

Frequency-resolved measurement of the orbital angular momentum spectrum of femtosecond ultra-broadband optical-vortex pulses based on field reconstruction

“…For applications such as quantum information processing or ultrafast nonlinear spectroscopy by ultrashort OV pulses [17], frequency-resolved measurement of OAM spectrum and evaluation of topological-charge dispersion is crucial. In addition, determining the relative phases between electric-field amplitudes of each m component, which is important for evaluating OVs or OV pulses with arbitrarily superposed modes [26][27][28], is also quite difficult with previous methods.In the present paper, we demonstrate an interferometric method of measurement of the OAM spectrum of ultra-broadband OV pulses based on field reconstruction by using the spatial Fourier transform. Our new method overcomes the drawbacks, such as angular dispersions for ultra-broadband pulses, of previous topological charge measurement methods.…”

Helicity control of a 2-μm optical vortex output from a vortex-pumped optical parametric oscillator

“…To date, we have successfully demonstrated a tunable, milli-joule-level mid-infrared (2-μm) vortex output from a 1-µm optical vortex pumped optical parametric oscillator (mid-infrared vortex laser), formed of a nonlinear crystal, KTiOPO 4 (KTP) [7,8]. However, our previous work concerning a mid-infrared optical vortex was focused only on the magnitude of the topological charge of the mid-infrared vortex output, and paid little attention to the wavefront helicity of the vortex output.…”