Membrane or film gain mediums have attracted great attention for their good thermal performances and light field manipulation properties, which are helpful for the power scaling of a laser. A membrane laser enabled on the waveguide grating structure is proposed and this design is flexible to manipulate optical properties by controlling the photonic density of states. Lasing behavior is theoretically analyzed based on the four-level rate equations. Results show that pump absorption is enhanced by about 35 times, which leads to improved laser efficiency. When the laser mode overlaps the resonant guided mode, the Purcell factor achieves 212, leading to enhanced emission rate, as well as an apparent decrease of relaxation oscillating amplitude and time delay. The present work offers a preliminary design and lasing behavior analysis of the vertical external surface-emission laser enabled on the waveguide grating structure.
Ring or conical light beams show great potential in many applications. We report on achievement of multi-ring-shaped conical beams through degenerated optical parametric generation (OPG) with tightly focused Gaussian pump beam in periodic polarized lithium niobate (PPLN) crystal. We observed continuous beam spatial pattern variation from multi to single ring and normal non-hollow beams by crystal temperature tuning. We attributed the experimental results to the effective polarized period changing under tightly focusing. This unique feature would exist in any quasi-phase matching processes and may find applications in optical trapping, manipulation, and even quantum field.
Based on the polarization period of 11.73um magnesium-oxide-doped lithium niobate (MgO: PPLN) Crystal, frequency up-conversion of continuous-wave (CW) 1559.5nm signal light has been demonstrated. It is pumped with an actively Qswitched diode-pumped Nd: YAG laser at 1064nm in micro cavity scheme. When operating at the temperature of 110.3 °C, the wavelength of output light is 632.5nm, and the maximum energy conversion efficiency is 1.1×10-4. The change of the output light characteristic as the operating temperature varies is studied, and the beam quality of the output laser is also analyzed.
The upconversion of an orbital angular momentum (OAM) carried light in communication band is preferable for building OAM-based upconversion optical communication networks. Here we experimentally study the behavior of OAM of communication band light in sum frequency generation process. The wavelength of the pump beam with sub-nanosecond pumping fields is 1064 nm and the communication band light is 1560 nm. Both beams are imprinted with OAM using vortex phase plates.The topological charges of the upconversion pulses at 632.5 nm are observed by a self-referenced interferometric technique. The OAM conserves in coupled nonlinear optical conversions is confirmed by counting the fringes in the interference intensity profile.The sum frequency generation is performed by using a periodically poled MgO-doped lithium niobate (PPLN) crystal under quasi-phase-matching conditions. We also gave analytical expressions for the upconversion of two OAM-carrying beams. The experimental results are well matched with the theoretical simulations.
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