Erbium-ytterbium waveguide laser mode-locked with a semiconductorsaturable absorber mirror

Picosecond pulses are produced using a semiconductor saturable absorber mirror in a laser based on an Er-Yb codoped planar waveguide amplifier. Continuous-wave mode-locking (CWML) with 9.8-ps pulses is obtained at repetition rates up to 100 MHz. With intracavity spectral filtering, saturable pulsewidths of 1 ps are achieved, and tunable picosecond pulses are obtained from 1534 to 1553 nm. Absorber characterization suggests that two-photon absorption within the saturable absorber mirror influences the CWML stability     

Generation and dynamics of special mode-locked pulses in an ultrafast Er-doped fiber laser with SMF-GIMF-SMF saturable absorber

<正>In this paper, we have demonstrated an Er-doped ultrafast laser with a single mode fiber-gradient index multimode fiber-single mode fiber(SMF-GIMF-SMF, SMS) structure as saturable absorber(SA), which can generate not only stable single-pulse state, but also special mode-locked pulses with the characteristics of high energy and noisy behaviors at proper pump power and cavity polarization state. In addition, we have deeply investigated the real-time spectral evolutions of the mode-locked pulses through the dispersive Fourier transformation(DFT) technique. It can be found that the pulse regime can actually consist of a lot of small noise pulses with randomly varying intensities. We believe that these results will further enrich the nonlinear dynamical processes in the ultrafast lasers.     

800nm布拉格反射镜型半导体可饱和吸收镜

我们在国内首先研制成功波长为800nm附近布拉格反射镜型半导体可饱和吸收镜。用布拉格反射镜型半导体可饱和吸收镜作为自启动装置，我们实现了氩离子激光器泵浦的钛宝石激光器被动连续锁模，获得了连续锁模脉冲序列，重复频率在100MHz到200MHz。     

Theory of mode-locked lasers containing a reverse saturable absorber

An analytic solution is presented for mode-locking a laser using a saturable absorber and reverse saturable absorber with long relaxation times compared to the temporal pulse widths. A reverse saturable absorber is a material with an excited-state absorption cross section larger than the ground-state absorption cross section, where increasing the incident light intensity increases the absorption. The reverse saturable absorber plays an important role in mode-locking laser materials where individual pulses cannot saturate the gain. A numerical example of mode-locking a CW alexandrite laser with a reverse saturable absorber and a saturable absorber is presented.     

Ultra-low repetition rate linear-cavity erbium-doped fibre laser modelocked with semiconductor saturable absorber mirror

Reported is an ultra-long linear-cavity erbium-doped fibre laser modelocked by a high modulation depth hybrid mirror-based semiconductor saturable absorber mirror with ultra-low repetition rate and highlychirped output pulses of high energy. With a repetition rate of 250.7 kHz, the laser delivers the single pulse energy of 14 nJ at a pump power of 430 mW. The minimum achievable repetition rate was as low as 25.4 kHz.     

230 fs, 25 W pulses from conventional mode-locked laser diodes with saturable absorber created by ion implantation

230 fs, 25 W pulses are obtained from conventional mode-locked AlGaAs laser diodes with highly-reflecting external cavities. Uncoated commercial diodes are used with a region of saturable absorption created by ion implantation. The overall pulse performances are believed to be among the best reported from simple electrically-pumped laser diodes without using additional amplifier sections.<>     

Tunable dual-wavelength ring fiber laser with stable output based on saturable absorber and thin core passive fiber

A dual-wavelength erbium-doped ring fiber laser is proposed and experimentally demonstrated though a detailed theoretical analysis and experimental verification. The proposed dual-wavelength erbium-doped fiber (EDF) laser, which is based on a ring fiber laser structure, is fabricated using two fiber Bragg gratings. By adjusting the gains and losses of the fiber laser structure, the laser can be switched between single- and double-wavelength modes. A saturable absorber (SA) is used to improve the output laser stability, which is further enhanced by splicing a thin core passive fiber (TCPF) into the laser cavity to produce a Mach–Zehnder filter effect. Optimizing the lengths of the SA and TCPF results in the adoption of a 1-m EDF and a 4-m passive fiber. On the basis of these enhancements and optimizations, a fiber laser with stable output is constructed that incurs single- or dual-wavelength laser shifts of less than 3 pm at room temperature over a period of 250 s.     

Stable single-frequency fiber ring laser for 25-GHz ITU-T grids utilizing saturable absorber filter

A stable single-frequency fiber ring laser is proposed that operates in a single mode for more than an hour by incorporating unpumped erbium-doped fiber (EDF) as a saturable absorber filter and optimizing the length of EDF used as gain medium. This laser can be continuously tuned to 25-GHz spacing that precisely matches the ITU-T grids by temperature control of etalon filter. This laser had a signal-to-source spontaneous emission ratio higher than 70 dB, and lasing frequencies of 361 channels was matched to ITU-T grids with excellent flatness. Frequency offset from the ITU-T grid was less than 0.14 GHz. The linewidth and the relative intensity noise value was less than 1.3 kHz and 130 dB/Hz (above 250 kHz), respectively.     

Fluctuation mechanism of ultrashort pulse generation by laser with saturable absorber

This paper presents a theoretical treatment of the fluctuation mechanism involved in the generation of picosecond laser pulses with saturable absorbers. The processes responsible for the shortening of the pulsewidth and for selection of the most intense pulse are treated. Some experimental results that confirmed the treatment are presented. The influence of inertia of saturable absorber and nonlinear losses (self-focusing and self-modulation) is discussed.     

Passively mode-locked Er3+ fiber laser using asemiconductor nonlinear mirror

A nonlinear mirror consisting of an InGaAs/InP multiple-quantum-well saturable absorber integrated with a Bragg reflector stack has been used to passively mode-lock a fiber laser in an extremely simple and advantageous linear-cavity configuration. To date, pulses as short as 7.6 ps have been observed     

Cr4+:YAG作饱和吸收体的被动Q开关复合单晶光纤激光器

采用激光加热基座法(LHPG)将Cr4 :YAG单晶光纤和Nd3 :YAG单晶光纤生长为一体化复合单晶光纤。进一步实验研究该单晶光纤的一些性质,表明它满足全固化被动调Q激光器的要求。已实现了脉宽10ns、最大平均输出功率达30mW、重复频率为16kHz的调Q激光。     

Pulsing behavior of a three-level laser with saturable absorber

A numerical study of a three-level laser model that includes a saturable absorber is presented. The theory models the laser as a lumped element. This assumption is valid as long as the laser pulses are much longer than the cavity. The model is intended to be somewhat representative of an erbium-doped fiber laser without trying to mimic the operating parameters of such a laser too closely. As expected, the presence of the saturable absorber causes the laser to be unstable under certain operating conditions. The question of stability is explored by examining small perturbations of the steady-state solutions of the rate equations. It is found that the predictions of this stability analysis are in excellent agreement with the behavior of the solutions of the full time-dependent rate equations. It is also found that under certain conditions the laser may pass from pulsed to stable operation simply by raising the pump power     

用半导体吸收体实现陶瓷激光器被动锁模研究进展

新型陶瓷材料近年来开始作为激光增益材料,具有低成本、大尺寸、制备时间短、热导率高等优点。大功率飞秒激光器是近年来超短脉冲激光制备的一大热点。本文探讨了使用半导体可饱和吸收镜实现被动锁模大功率陶瓷飞秒激光器的可行性,研究现状以及未来趋势。     

Femtosecond Cr:forsterite laser with mode locking initiated by aquantum-well saturable absorber

We studied a mode-locked Cr:forsterite laser pumped by a diode pumped Nd:YVO₄ laser. Both the Kerr lens mode locking and the semiconductor saturable absorber initiated mode locking have been demonstrated. Using our measured dispersion data of the forsterite crystal, together with our dispersion compensation technique, we obtained 20-fs pulses for the pure Kerr lens mode locking and 36-fs pulses for semiconductor saturable absorber initiated mode locking, respectively     

Feedback stabilized actively mode-locked Nd:phosphate glass laser

An electrooptic, actively mode-locked Nd: phosphate glass laser system is described employing a novel single-step feedback system to stabilize the pulse buildup time. Single output pulses of ∼100 ps duration with energies of up to 1 mJ could be reliably generated with a standard deviation in thesim3.2 mus pulse buildup time of ±40 ns allowing synchronization with pulses from laser systems at other wavelengths. Evidence of pulse broading due to self-phase modulation was observed together with wide tunability of the output wavelength from 1.054 to 1.068 μm.     

Nanosecond pulse generation in a passively Q-switched Yb-doped fiber laser by Cr/sup 4+/:YAG saturable absorber

We explored efficient nanosecond pulse generation in a passively Q-switched cladding-pumped Yb-doped fiber laser by use of an external-cavity configuration containing a Cr/sup 4+/:YAG saturable absorber crystal. By exploiting passive Q-switched regime and stimulated Brillouin scattering, pulses of durations as short as 2.7 ns, corresponding to a peak power of /spl sim/9 kW, have been achieved. The laser was tunable over 70 nm and green output power generation was obtained by external frequency doubling in a KTP crystal.     

Passive mode locking in a diode-pumped Nd:GdVO/sub 4/ laser with a semiconductor saturable absorber mirror

We demonstrate Q-switched and CW passive mode locking in a laser-diode-pumped Nd:GdVO/sub 4/ laser with a semiconductor saturable absorber mirror. The repetition rate of the Q-switched envelope increased from 23.1 to 260 kHz as the pump power increased from 1.75 to 13.0 W. At a pump power of 13.7 W, the Q-switched mode locking changed to CW mode locking. The maximum average output power of 4.9 W with a 140-MHz repetition rate was obtained at a pump power of 17.9 W and the single mode-locked pulse energy was 0.035 /spl mu/J. The CW mode-locked pulse duration was measured to be /spl sim/11.5 ps.     

Harmonically mode-locked fiber laser with optically selectablewavelength

In this letter, we demonstrate optical selection of wavelength in a harmonically mode-locked fiber laser that incorporates a semiconductor optical amplifier nonlinear fiber loop. Wavelength tuning is achieved by controlling the delay time between the modulation and the control signals in the compensated dispersion-tuning scheme. A tuning range over 19 nm is obtained. The power suppression of nonlasing modes reaches a maximum of 34 dB. The output wavelength and the delay time are governed by a linear relationship