Tunable-wavelength picosecond vortex generation in fiber and its application in frequency-doubled vortex

Abstract

We present a method for tunable-wavelength picosecond vortex pulse generation by using an acoustically-induced fiber grating (AIFG). The AIFG-driven mode conversion characteristic was activated via a shear-mode piezoelectric transducer that excels in excitation efficiency of acoustic flexural wave and mechanical stability. The linearly-polarized ±1-order picosecond vortex pulse was experimentally generated via AIFG with a uniform coupling efficiency of ∼98.4% from the fundamental mode to the ±1-order vortex mode within the wavelength range 1540 nm ∼ 1560 nm. The topological charge and the linearly-polarized characteristic of the picosecond vortex pulse were verified by examination of the off-axial interference and the polarization angle-dependent intensity, respectively. Furthermore, the picosecond vortex pulse with wavelength tunability was input to a nonlinear BBO crystal to generate a frequency-doubled ±2-order vortex in the wavelength range 770 nm ∼ 780 nm. This technology provides a convenient apparatus for generating a picosecond vortex pulse and the frequency-doubled vortex with wavelength tunability.

Recent progress of dynamic mode manipulation via acousto-optic interactions in few-mode fiber lasers: mechanism, device and applications

“…It is found that extra-cavity AOMCs can also demonstrate the OAM generations from a fundamental mode ultrafast pulsed laser [91,136]. Figure 12A and B ( Figure 12C and D) delivers the experimental configuration and the corresponding results of femtosecond (picosecond) pulsed OAM generation, respectively.…”

“…The pioneered discovery in 1986 that Kim et al firstly proposed and demonstrated the mode conversion with a frequency shift by a two-mode fiber-based AOMC [43], which has opened a door to novel researches on acousto-optic interactions (AOI) in fibers and various derived components. Among them, the most extensively concerned are tunable filters [51][52][53][54][55][56][57][58][59][60][61][62][63][64], super lattice modulations [65][66][67][68][69], heterodyne vibration detections [70][71][72][73], AOI in photonic crystal fibers (PCFs) [74][75][76][77], wavelength tunable lasers [78][79][80][81][82], ultrafast fiber lasers based on AOMCs [83][84][85][86][87][88][89][90][91][92], vector modes generations [93][94][95]...…”

Generation of polarization and phase singular beams in fibers and fiber lasers

“…For example, complex polarized CVBs and high-order VBs (l > 3) are difficult to be formed in few-mode fiber unless using specially designed fibers. [141][142][143] CVBs and VBs formed in fibers and fiber lasers have found lots of special applications, such as nonlinear frequency conversion, [144][145][146] flattop beam generation, 147 quantum entanglement, 148 optical micromanipulation, 149,150 stimulated emission depletion (STED) microscopy, 151 optical sensing, 152 and mode-division multiplexing. 61,95,133 Furthermore, we have theoretically and experimentally presented the nanofocusing characteristic of several metal-coated fiber tips under RPB excitation in the visible band, providing an effective guideline for designing the background-free tip-enhanced Raman spectroscopy system.…”

High-power fiber laser with real-time mode switchability

“…In fact, there are several approaches to realizing mode adjusting/switching in fiber lasers [12] , and technically an 'optical switch' combined with mode selective components should be adopted. The mode switching/adjusting operation could either be realized by real optical components, such as acoustic-optic tunable filter (AOTF) [13] , special fiber coupler [14][15][16][17] , acoustically induced fiber grating (AIFG) [18][19][20][21] , polarization controller (PC) [22][23][24][25][26][27] , and spatial light modulator [28] , or by some physical mechanisms, such as temperature control of few-mode fiber Bragg gratings (FBGs) [29] , altering the excitation condition [30] , and injection locking [31] . However, fast mode switching between different transverse modes in fiber lasers has only been demonstrated using AOTF and AIFG.…”