Yen Cheng Fang

Passively Q-switched erbium all-fiber lasers by use of thulium-doped saturable-absorber fibers

We demonstrate all-fiber passively Q-switched erbium lasers at 1570 nm using Tm(3+)-doped saturable-absorber fibers. The absorption cross section of a Tm(3+)-doped fiber at 1570 nm was measured in a bleaching experiment to be about 1.44 x 10(-20) cm(2). With a thulium-doped fiber, sequential pulses with a pulse energy of 9 microJ and a pulse duration of about 420 ns were stably produced at repetition rates in the range 0.1 to 2 kHz. The maximum pulse repetition rate was 6 kHz, limited by the maximum pump power of a 980-nm laser diode, about 230 mW.

A saturable absorber Q-switched all-fiber ring laser.

We propose a simple design of a saturable absorber Q-switched all-fiber ring laser. By locating a saturable absorber fiber in the intensity-enhanced section of a ring resonator, the laser is passively Q-switched. A set of location-dependent rate equations is established for Q-switching modeling. The design has been numerically and experimentally demonstrated using Er(3+)-doped fiber at the emission wavelength of 1550 nm. A single-mode Q-switched pulse with pulse energy of 0.37 microJ and pulse duration of 218 ns was achieved with 980-nm pump power near 7 mW.

All-fiber passively Q -switched erbium laser using mismatch of mode field areas and a saturable-amplifier pump switch

We propose and demonstrate an all-fiber self-Q-switched erbium laser system that is saturable-absorber Q switched by the mismatch of the mode-field areas in the resonator and stabilized with a saturable-amplifier pump switch. Sequential pulses with a pulse energy of 8-6 microJ and a pulse duration of 80-320 ns, corresponding to a pulse repetition rate of 0.25-1 kHz, were obtained using a cw 980 nm laser-diode pump. A peak pulse power of near 100 W was achieved.

Saturable absorber Q- and gain-switched all-Yb3+ all-fiber laser at 976 and 1064 nm.

We demonstrate a novel passively pulsed all-Yb3+ all-fiber laser pumped by a continuous-wave 915-nm pump laser diode. The laser was saturable absorber Q-switched at 976 nm and gain-switched at 1064 nm, using the method of mode-field-area mismatch. With a pump power of 
105 mW, the laser iteratively produced a 976-nm pulse with an energy of 2.8 μJ and a duration of 280 ns, followed by a 1064-nm pulse with 1.1 μJ and a 430-ns duration at a repetition rate of 9 kHz. A set of rate equations was established to simulate the self-balancing mechanism and the correlation between the Q- and gain-switched photon numbers and the populations of the gain and absorber fibers.

A novel ultracompact two-mode-interference wavelength division multiplexer for 1.5-/spl mu/m operation

A novel ultracompact 2/spl times/2 wavelength division multiplexer (WDM) for 1.55-/spl mu/m operation based on highly dispersive two-mode interference (TMI) was designed, theoretically modeled, and verified using a finite-difference-time-domain (FDTD) method. A two-moded waveguide assisted with a dispersive tooth-shaped grating provided a mode-dependent reflection band of central wavelength at 1.55 /spl mu/m. The wavelengths of 1538 and 1572 nm that were at the band edges and had the lowest reflection losses and relatively high dispersion were selected for wavelength multiplexing. The result showed that the wavelengths were separated by grating dispersion in a coupler length of 75 /spl mu/m which was much shorter than the required length of 1.1 mm in a regular TMI multiplexer of no grating. Insertion loss of about 1.7 dB and channel contrast of about 12 dB were achieved.

A self-Q-switched all-fiber erbium laser at 1530 nm using an auxiliary 1570-nm erbium laser.

We demonstrate a self-Q-switched, all-fiber, tunable, erbium laser at 1530 nm with high pulse repetition rates of 0.9-10 kHz. Through the use of an auxiliary 10-mW, 1570 nm laser that shortened the relaxation time of erbium, sequentially Q-switched pulses with pulse energies between 4 and 6 microJ and pulse widths of 40 ns were steadily achieved. A peak pulse power of 165 W was obtained.

Passively cascade-pulsed erbium ZBLAN all-fiber laser

We propose and numerically demonstrate a cascade pulsing mechanism in a CW-pumped Er³⁺:ZBLAN all-fiber laser system. In the design, the laser was pumped at 980 nm and passively Q-switched at 1.6 μm. The Q-switched resonance reduced the population on ⁴/13/2 of the erbium gain fiber, thereby creating a population inversion between the levels of 4/11/2 and ⁴/13/2, and instantly inducing an intense gain-switched pulse at 2.7 μm. Sequential 2.7-μm single-mode pulsing with a pulse energy of 170 μJ and a peak power of 6 kW was achieved with an absorbed pump power of 0.65 W.

Self-balanced Q- and gain-switched erbium all-fiber laser

We demonstrate a 980-nm CW-pumped fully passive pulsed all-Er3+ all-fiber laser, self-balancing between being Q- and gain-switched at S and L bands. The laser was passively Q-switched at 1510 nm with the saturable absorber in an intra-cavity gain-switched at 1570 nm. The time spacing between the Q- and gain-switched pulse peaks was steadily 0.92 or 2.75 μs depending on the absorber lengths. Sequential 1510-nm pulsing with a pulse energy of 3.8 μJ and a pulse width of 280 ns at a repetition rate of 1.7 kHz was achieved with a pump power of 175 mW.