Flexible generation of femtosecond cylindrical vector beams (Invited Paper)

Abstract

Femtosecond (fs) cylindrical vector beams (CVBs) have found use in many applications in recent years. However, the existing rigid generation methods seriously limit its development. Here, we propose a flexible method for generating fs-CVBs with arbitrary polarization order by employing half wave plates and vortex retarders. The polarization state, autocorrelation width, pulse width, and spectrum features of the input and generated CVB pulses are measured and compared. The results verify that the generated CVBs remain in the fs regime with no appreciable temporal distortion, and the energy conversion efficiency can reach as high as 96.5%, even for a third-order beam. As a flexible way to generate fs-CVBs, this method will have great significance for many applications.OCIS codes: 260.5430, 320.2250. doi: 10.3788/COL201715.030007.Cylindrical vector beams (CVBs) have gained much interest because of their unique polarization properties [1,2] . They have been widely applied and play an important role in many optical fields, such as optical trapping [3][4][5] , optical communications [6,7] , laser fabrication [8] , imaging [9,10] , and sensing [11] . In recent years, CVBs in the femtosecond (fs) field have been widely applied in processing, optical limiting, etc. [12][13][14][15] , as a result of advantages that include ultrahigh peak power and ultrafast pulses. Generation of fs-CVBs has great importance for many fields of research and applications [16][17][18][19][20][21] . For the generation of common CVBs, many methods have been proposed, including inserting laser intracavity devices [22][23][24] or applying devices with spatially variant polarization properties [25][26][27][28] , such as Q-plate, axial birefringence, and dichroism. However, in these methods, high flexibility and energy efficiency are usually mutually exclusive, and a pulse width broadening is inevitable. Meanwhile, the processing difficulty sharply increases with higher polarization orders of CVBs, as polarization exhibits more complex spatial inhomogeneous distribution with increased orders [24] . In this work, fs-CVBs with an arbitrary order were flexibly generated with high energy efficiency and pure polarization properties from a linearly polarized beam by employing combined vortex retarders (VRs, Thorlabs Inc.) and half wave (1∕2λ) plates. Higher-order fs-CVBs, with odd and even, negative and positive orders, were experimentally generated by cascading VRs and 1∕2λ plates. The polarization, autocorrelation width, pulse width, and spectrum features of the original and generated pulse were measured and detected. The results verified that the fs-CVBs have a perfect polarization quality and remain in the fs regime with no appreciable temporal distortion. In addition, the energy conversion efficiency is higher than 96.5% for order of 3. This method is therefore verified as a flexible way to generate CVBs with arbitrary orders, and it will be a significant method for fs-CVBs' research in the future.The schematic of the fs-CVBs' generation setup is sh...

Two-channel, dual-beam-mode, wavelength-tunable femtosecond optical parametric oscillator

“…2(b), the reversible light transformation process is derived using Jones matrices. 20 To characterize the proposed dual-channel OPO, we initially performed wavelength measurement by tuning the cavity length of each channel individually, as commonly used in femtosecond laser pumped OPOs. 21 It should be noted that coherent coupling between two signals is completely avoided as a result of the cavity design.…”

A succinct method to generate multi-type HCV beams with a spatial spiral varying retardation-plate

“…Many methods have been proposed to generate CV beams, including special optical elements in a laser cavity [17,18], segmented waveplates [19][20][21], interferometric (a) E-mail: whwang@ipp.ac.cn (b) E-mail: xjli@nudt.edu.cn technique [22,23], liquid-crystal spatial light modulators [24][25][26], special gratings [27,28] and fibers [29,30]. Of these, there are different degrees of stability, complexity, efficiency, flexibility and intensity.…”