本論文研究被動Q-開關Nd:GdVO4雷射的圓柱向量偏振行為。在三面鏡系統的架構下，將輸出耦合鏡往穩定區的邊界移動，可以看到雷射輸出由Gaussian mode轉變成Ring mode。同時在Ring mode範圍內可觀察到方位角和徑向偏振。隨後我們在腔內加入一飽和吸收體，產生Q-開關脈衝，並比較脈衝和連續波這兩種條件下的圓柱向量偏振行為。實驗結果顯示飽和吸收體的加入會減小Ring mode的圓柱向量偏振範圍，但我們仍可得到有高偏振比的圓柱向量偏振脈衝。

Radially and azimuthally polarized beams were generated in passively Q-switched Nd:GdVO4 laser with a Cr:YAG saturable absorber. Based on the cavity design, the cavity configuration simultaneously satisfied the thereshold of the passive Q-switching and the generating condition of the cylindrical vector beam. When the pump power was 5W, the pulse width, repetition frequency, and the average power were 110 ns, 12.3 kHz, and 270 mW, respectively. The pulse operation had better polarization ratio than that of continuous-wave operation. Moreover, the spatial-dependent pulse trains were explored, and the dynamical behavior is an interesting future work.

[1] V. G. Niziev and A. V. Nesterov “Influence of beam polarization on laser cutting efficiency”, J. Phys. D 32, 1455(1999).
[2] M. Meier, V. Romano, and T. Feurer “material processing with pulsed radially and azimuthally polarized laser radiation”, Appl. Phys. A 86,329 (2007).
[3] D. P. Biss, K. S. Youngworth, and T. G. Brown “Dark-field imaging with cylindrical-vector beams”, Appl.Opt. 45, 470 (2006).
[4] K. S. Youngworth and T. G. Brown “ Inhomogenous polarization in scanning optical microscopy”, Proc. SPIE 3919,75 (2000).
[5] W. D. Kimura, G. H. Kim, R. D. Romea, L. C.Steinhauer, I. V. Pogorelsky, K. P. Kusche, R. C.Fernow, X. Wang, and Y. Liu “ Laser Acceleration of Relativistic Electrons Using the Inverse Cherenkov Effect” , Phys. Rev. Lett. 74, 546(1995).
[6] Q. Zhan “ Trapping metallic Rayleigh particles with radial polarization”, Opt. Express 12, 3377 (2004).
[7] H. Kavauchi, K. Yonezawa, Y. Kozawa, and S. Sato “Calculation of optical trapping forces on a dielectric sphere in the ray optics regime produced by a radially polarized laser beam”, Opt.Lett. 32, 1839 (2007).
[8] S. Quabis, R. Dorn, M. Eberler, O. Gloeckl, and G.Leuchs “Focusing light to a tighter spot”, Opt. Commun. 179, 1 (2000).
[9] S. C. Tidwell, G. H. Kim, and W. D. Kimura “Efficient radially polarized laser beam generation with a double interferometer”, Appl. Opt.32, 5222 (1993).
[10] G. Volpe, and D. Petrov “Generation of cylindrical vector beams with few-mode fibers excited by Laguerre–Gaussian beams”, Opt. Commun. 237, 89 (2004).
[11] H. Kawauchi, Y. Kozawa, S. Sato, T. Sato, and S.Kawakami “ Simultaneous generation of helical beams with linear and radial polarization by use of a segmented half-wave plate”, Opt. Lett. 33, 399 (2008).
[12] Y. Mushiake, K. Matsumura, and N. Nakajima “ Generation of radially polarized optical beam mode by laser oscillation”, Proc.IEEE 60, 1107 (1972).
[13] D. Pohl “ Operation of a Ruby Laser in the Purely Transverse Electric Mode TE01”, Appl. Phys. Lett. 20, 266 (1972).
[14] T. Moser, M. A. Ahmed, F. Pigeon, O. Parriaux, E.Wyss, and T. Graf “ Generation of radially polarized beams in Nd:YAG lasers with polarization selective mirrors” , Laser Phys. Lett. 1, 234 (2004).
[15] J.-F. Bisson, J. Li, K. Ueda, and Y. Senatsky “ Radially polarized ring and arc beams of a neodymium laser with an intra-cavity axicon ”, Opt.Express 14, 3304 (2006).
[16] Y. Kozawa and S. Sato “ Generation of a radially polarized laser beam by use of a conical Brewster prism”, Opt. Lett. 30, 3063 (2005).
[17] Y. Kozawa, S. Sato, T. Sato, Y. Inoue, Y. Ohtera, and S.Kawakami “Cylindrical Vector Laser Beam Generated by the Use of a Photonic Crystal Mirror”, Appl. Phys. Express 1, 022008 (2008).
[18] J. L. Li, K. I. Ueda, M. Musha, L. X. Zhong, and A. Shirakawa “ Radially polarized and pulsed output from passively Q-switched Nd:YAG ceramic microchip laser”, Opt. Lett. 33, 2686 (2008).
[19] F. Enderli and T. Feurer “ Radially Polarized Mode-locked Nd:YAG Laser”, Opt. Lett. 34, 2030 (2009).
[20] W. Koechner, Solid State Laser Engineering, 6th ed.(Springer, 2006)
[21] R. Weber, B. Neuenschwander, M. Mac Donald, M. B.Roos, and H. P. Weber “ Cooling schemes for longitudinally diode laser-pumped Nd:YAG rods ” ,IEEE J. Quantum Electron. 34,1047 (1998).
[22] Manasadevi P. Thirugnanasambandam, Yuri Senatsky, and K. Ueda “ Generation of radially and azimuthally polarized beams in Yb:YAG laser with intra-cavity lens and birefringent crystal”, OPTICS EXPRESS. Vol. 19, No. 3,1905 (2011).
[23] Ram Oron, Shmuel Blit, Nir Davidson, Asher A. Friesem, Zeev Bomzon et al. “ The formation of laser beams with pure azimuthal or radial polarization”, Appl. Phys. Lett. 77, 3322 (2000);
[24]J. B. Khurgin, F. Jin, G. Solyar, C. C. Wang and S. Trivedi “ Cost-effective low timing jitter passively Q-switched diode-pumped solid-state laser with composite pumping pulses”, Appl. Opt. 41, 1095 (2002).
[25] Z. Burshtein, P. Blau,Y. Kalisky, Y. Shimony, and M. R. Kokta “ Excited-state absorption studies of Cr ions in several garnet host crystals”, IEEE J. Quantum Electron., vol. 34, pp. 292–299, 1998.
[26] A. E. Siegman, Laser. Mill Valley, CA: Univ. Science, 1986, p.1012,1024.