Semiconductor Saturable Absorber Mirror Research Articles

Diode-pumped passively mode-locked femtosecond Yb:YLF laser at 1.1 GHz

We report femtosecond pulse generation at GHz repetition rates with the Yb:YLF gain medium for the first time. A simple, low-cost, and compact architecture is implemented for the potential usage of the system as a low-noise timing jitter source. The system is pumped by 250 mW, 960 nm single-mode diodes from both sides. The semiconductor saturable absorber mirror (SESAM) mode-locked laser is self-starting and generates transform-limited 210 fs long pulses near 1050 nm. The laser's average output power is 40 mW, corresponding to a pulse energy of 36 pJ at 1.1 GHz repetition rate. The measured laser relative intensity noise (RIN) from 1 Hz to 1 MHz is 0.42%. The performance obtained in this initial work is limited by the specifications of the available optics and could be improved significantly by employing custom-designed optical elements.

Upconversion-pumped femtosecond thulium laser at 2309 nm mode-locked by a GaSb-based SESAM

We report on a femtosecond thulium laser operating on the 3H4 → 3H5 transition with upconversion pumping around 1 µm and passively mode-locked by a GaSb-based SEmiconductor Saturable Absorber Mirror (SESAM). This laser employs a 6 at.% Tm:LiYF4 laser crystal and a polarization maintaining Yb-fiber master oscillator power amplifier at 1043 nm as a pump source addressing the 3F4 → 3F2,3 excited-state absorption transition of Tm3+ ions. In the continuous-wave regime, the Tm-laser generates 616 mW at ∼2313 nm with a slope efficiency of 10.0% (vs. the incident pump power) and a linear polarization (π). By implementing a type-I SESAM with a single ternary strained In0.33Ga0.67Sb quantum well embedded in GaSb for sustaining and stabilizing the soliton pulse shaping, the self-starting mode-locked Tm-laser generated pulses as short as 870 fs at a central wavelength of 2309.4 nm corresponding to an average output power of 208 mW at a pulse repetition rate of 105.08 MHz and excellent mode-locking stability. The output power was scaled to 450 mW at the expense of a longer pulse duration of 1.93 ps. The nonlinear parameters of the SESAM are also reported.

Sub-100 fs pulses lasers from Yb:GdScO3 crystal based on semiconductor saturable absorber mirrors

Sub-100 fs laser pulses are generated in a Yb:GdScO3 passively mode-locked laser based on a semiconductor saturable absorber mirror. The laser operates in the continuous wave mode-locked state with a repetition frequency of 81 MHz and a pulse width of 98 fs. The output pulses exhibit a high signal-to-noise ratio of 60 dB in the radio-frequency spectra, with a central wavelength of 1064.4 nm and a full width at half maximum of 12.4 nm. This achievement marks the first successful demonstration of an ultrafast laser in a Yb:GdScO3 crystal, validating Yb:GdScO3 as an ideal medium for generating ultrafast lasers.

2.8-µm polarization-maintaining Er fiber laser mode-locked by a GaSb-based SESAM

A GaSb-based SEmiconductor Saturable Absorber Mirror (SESAM) enables continuous-wave picosecond mode-locked operation with excellent stability of a polarization-maintaining mid-infrared Er:ZBLAN fiber laser. The GaSb-based SESAM mode-locked fiber laser delivers an average output power of 190 mW at 2.76 µm at a repetition rate of 32.07 MHz (corresponding to a pulse energy of ∼6 nJ) and exhibits a high signal-to-noise ratio of ∼80 dB. The polarization extinction ratio is more than 23 dB. By employing an intracavity diffraction grating, the laser wavelength is continuously tunable across 2.706–2.816 µm. Passively Q-switched operation of this laser is also demonstrated.

Diode-pumped 88 fs SESAM mode-locked Tm,Ho:CLNGG laser at 2090 nm

We report on a passively mode-locked Tm,Ho:CLNGG laser operating at 2090 nm, pumped by a multimode fiber-coupled 793 nm laser diode, representing the first demonstration of a diode-pumped sub-100-fs mode-locked laser at 2.1 μm wavelength. Due to the disordered nature of the gain material that exhibits a broad and smooth gain profile, pulses as short as 88 fs were achieved with an average output power of 120 mW at a repetition rate of 70.3 MHz. Stable self-starting mode-locked operation was obtained using a semiconductor saturable absorber mirror based on the GaSb material system.

Femtosecond pulse generation from a semiconductor saturable absorber mirror mode-locked Yb:LuYAG mixed crystal laser

We report on a femtosecond semiconductor saturable absorber mirror (SESAM) mode-locked Yb:LuYAG laser. Pumped by a 976 nm single-mode fiber laser, a self-starting mode-locked Yb:LuYAG laser was demonstrated, delivering a 618-mW output power with 140-fs pulses and a 95.4-MHz repetition rate. The output spectrum is centered at 1053 nm with a spectral width of 10.4 nm. To the best of our knowledge, this is the shortest pulse ever generated from a mode-locked Yb:LuYAG laser.

Difference of carrier dynamics in a semiconductor saturable absorber mirror with and without B+ ion-implantation.

Three samples whose growth temperatures were 450°C, 500°C, and 560°C for S E S A M 1, S E S A M 2, and S E S A M 3, respectively, were tested by femto-second time-resolved transient absorption spectroscopy. The results indicate that the carrier dynamics of excited state absorption were dominant, and the lifetimes of carriers trapped by defect levels were about tens of pico-seconds. To further study the influence of carrier dynamics and recovery time of samples by ion-implantation, B + ions of 80 and 130 KeV were implanted into the samples with dose of 1014/c m 2. The modified samples showed a dominance of ultra-fast carrier dynamics of ground-state bleaching and direct recombination, which lasted for hundreds of femto-seconds, over excited state absorption. Additionally, carrier fast trapping was observed to be competitive with the excited state absorption process. After ion-implantation, the carrier dynamics of carrier trapping were enhanced, which contributed to forming an ultra-short laser, while the carrier dynamics of absorption of the excited state were suppressed. The conclusion that defect levels were partially eliminated by B + ion-implantation can be drawn.

SESAM mode-locked Yb:GdScO3 laser.

We report on the investigation of continuous-wave (CW) and SEmiconductor Saturable Absorber Mirror (SESAM) mode-locked operation of a Yb:GdScO3 laser. Using a single-transverse-mode, fiber-coupled InGaAs laser diode at 976 nm as a pump source, the Yb:GdScO3 laser delivers 343 mW output power at 1062 nm in the CW regime, which corresponds to a slope efficiency of 52%. Continuous tuning is possible across a wavelength range of 84 nm (1027-1111 nm). Using a commercial SESAM to initiate mode-locking and stabilize soliton-type pulse shaping, the Yb:GdScO3 laser produces pulses as short as 42 fs at 1065.9 nm, with an average output power of 40 mW at 66.89 MHz. To the best of our knowledge, this is the first demonstration of passively mode-locking with Yb:GdScO3 crystal.

Sub-60-fs mode-locked Tm,Ho:CaYLuAlO4 laser at 2.05 µm

Tm,Ho:CaYLuAlO4 (Tm,Ho:CALYLO) crystal has wide emission spectra both for π-polarization and σ-polarization, showing significant potential for the generation of ultrashort pulses. Here, a widely tunable and passively mode-locked laser operation based on Tm,Ho:CALYLO crystal under two polarizations was demonstrated for what we believe to be the first time ever. For π-polarization, a maximum output power of 1.52 W and a tuning range of 255.3 nm were achieved in the continuous wave (CW) regime. In the mode-locked regime, a pulse duration of 68 fs and an average output power of 228 mW were achieved upon GaSb-based semiconductor saturable absorber mirror (SESAM). As for σ-polarization, a broader tuning range of 267.1 nm was realized, leading to the shorter pulse duration of 58 fs at 79.7 MHz repetition rate.

Continuous-wave and SESAM mode-locked operation of a Yb:YSr3(PO4)3 laser.

We report on the continuous-wave (CW) and, for what we believe to be the first time, passively mode-locked (ML) laser operation of an Yb3+-doped YSr3(PO4)3 crystal. Utilizing a 976-nm spatially single-mode, fiber-coupled laser diode as pump source, the Yb:YSr3(PO4)3 laser delivers a maximum CW output power of 333 mW at 1045.8 nm with an optical efficiency of 55.7% and a slope efficiency of 60.9%. Employing a quartz-based Lyot filter, an impressive wavelength tuning range of 97 nm at the zero level was achieved in the CW regime, spanning from 1007 nm to 1104 nm. In the ML regime, incorporating a commercially available semiconductor saturable absorber mirror (SESAM) to initiate and maintain soliton-like pulse shaping, the Yb:YSr3(PO4)3 laser generated pulses as short as 61 fs at 1062.7 nm, with an average output power of 38 mW at a repetition rate of ∼66.7 MHz.

Growth, spectroscopy and SESAM mode-locking of a "mixed" Yb:Ca(Gd,Y)AlO4 disordered crystal.

We present the growth, spectroscopy, continuous-wave (CW) and passively mode-locked (ML) operation of a novel "mixed" tetragonal calcium rare-earth aluminate crystal, Yb3+:Ca(Gd,Y)AlO4. The absorption, stimulated-emission, and gain cross-sections are derived for π and σ polarizations. The laser performance of a c-cut Yb:Ca(Gd,Y)AlO4 crystal is studied using a spatially single-mode, 976-nm fiber-coupled laser diode as a pump source. A maximum output power of 347 mW is obtained in the CW regime with a slope efficiency of 48.9%. The emission wavelength is continuously tunable across 90 nm (1010 - 1100 nm) using a quartz-based Lyot filter. With a commercial SEmiconductor Saturable Absorber Mirror to initiate and maintain ML operation, soliton pulses as short as 35 fs are generated at 1059.8 nm with an average output power of 51 mW at ∼65.95 MHz. The average output power can be scaled to 105 mW for slightly longer pulses of 42 fs at 1063.5 nm.

Mode-locked Yb:CALGO laser with high peak power sub-100 fs pulses at 26.9 MHz repetition rate

The development of a diode-pumped high peak power sub-100 fs mode-locked Yb:CALGO laser is presented. The laser delivered 1.3 W of output power with 81 fs pulses at a repetition rate of 26.9 MHz. The corresponding pulse energy was 48 nJ and the peak power was 596 kW. The cavity was extended by using a 1:1 imaging telescope. Mode locking was based on a semiconductor saturable absorber mirror and chirped mirrors were used to compensate for the positive dispersion in the cavity. To the best of our knowledge, this is one of the shortest pulse durations obtained from Yb:CALGO laser around this low repetition rate.

Experimental characterization of quasiperiodic route to chaos in a VECSEL with SESAM

We analyze the temporal dynamics of an optically-pumped quantum well vertical external-cavity surface-emitting laser (VECSEL) with a Semiconductor Saturable Absorber Mirror (SESAM) using the time series obtained when varying the pump power. We unveil the quasiperiodic route to chaos in the system by characterizing the Fourier spectra, the attractors in phase space, and the Lyapunov exponents for each temporal behavior observed: periodicity, quasiperiodicity, and chaos. Thus, we provide a complete description of this experimental observation of the route to chaos in a VECSEL-SESAM system.

Low repetition rate passively mode-locked semiconductor disk laser

Semiconductor disk lasers (SDLs) have advantages of high output power and good beam quality. Its flexible external cavity provides convenience for inserting additional optical element to start mode locking and produce ultra-short pulse train with duration from picosecond to femtosecond. However, the very short lifetime of about a few nanoseconds to tens of nanosecond of the carrier in semiconductor gain medium limits the decrease of pulse repetition rate, thus restrict the increase of peak power of the mode-locked laser pulse to some extent. In this work, by using the relatively shallow In0.2GaAs quantum wells, which has a relatively long carrier lifetime in the active region of gain chip, as well as the particularly designed semiconductor saturable absorption mirror (SESAM) that with a relatively small saturation flux, a passively mode-locked SDL with low repetition rate and high peak power is demonstrated. The used six-mirror cavity has a spot radius of about 200 μm on the chip and a 40 μm spot on the SESAM, and the total cavity length is about of 1.92 m. The SESAM passively mode-locked SDL produces a stable pulses train with the lowest repetition rate of 78 MHz. When the temperature is 12℃ and the transmittance of the output coupler is T = 3%, an average output power of 2.1 W and a pulse duration of 2.08 ps are achieved. The corresponding pulse peak power reaches 12.8 kW, which is about twice of the reported highest peak power in a SESAM mode-locked SDL. When T = 2% and T = 5%, the obtained average output power are 1.34 W and 1.62 W respectively, and the corresponding pulse peak power are 8.17 kW and 9.88 kW. Based on the reported literatures and the results of pulse repetition rate in our experiments, the estimated lifetime of the carriers of the In0.2GaAs quantum wells in the active region of the gain used chip is 16.4 ns. This high peak power mode-locked semiconductor disk laser has important potential applications in biomedical photonics, chemistry, and nonlinear microscopy.

Femtosecond pulsed laser technology and applications

This paper describes femtosecond pulsed laser technology and related applications. The focus is on two core femtosecond pulsed laser technologies: femtosecond pulsed laser generation and amplification. In the generation of femtosecond pulsed lasers, mode-locking techniques, Kerr-lens mode-locking, and semiconductor saturable absorber mirrors are presented; in the amplification of femtosecond pulsed lasers, chirped-pulse amplification and coherent synthesis techniques are presented. This paper analyses the applications of femtosecond pulsed lasers in both the biomedical and manufacturing sectors and gives the development trends as well as the challenges of femtosecond laser technology. Femtosecond lasers are now used in a wide range of applications. Femtosecond pulsed lasers will develop in the directions of high power, miniaturisation, intelligence and precision. Laser tweezers will become the new direction of development in the future.

Soliton rain in all-polarization-maintaining mode locked fiber laser.

For the first time the phenomenon of soliton rain is observed in a mode-locked fiber laser with all-polarization-maintaining (all-PM) architecture. The laser is mode-locked using a semiconductor saturable absorber mirror (SESAM) and operates in the all-normal dispersion (ANDi) regime. The operation state of the laser can be switched from dissipative soliton to soliton rain by simply raising the pump power, without any manipulation of the intracavity polarization state given that all components of the resonator are made of PM fibers. The soliton rain generated in the laser is self-starting and replicable, since it occurs in every individual operation of the laser as the pump power is increased to an approximately invariant value.

Dual-parameter femtosecond mode-locking pulse generation in partially shared all-polarization-maintaining fiber Y-shaped oscillator with a single saturable absorber

We present a design of a mode-locked fiber laser based on a polarization-maintaining (PM) Y-shaped fiber structure, which employs a single semiconductor saturable absorber mirror (SESAM) and a common polarization beam combiner (PBC) to achieve dual- parameter mode-locking femtosecond pulse in two orthogonal polarization states. The two output pulses have different characteristics, such as repetition frequency (87.3 MHz and 91.3 MHz), average output powers (2.1 mW and 1.9 mW), pulse durations (299 fs and 377 fs) and spectral profiles (centered at 1565.6 nm and 1563.6 nm with spectral width of 9.96 nm and 9.93 nm). The properties of the two pulses are experimentally characterized and their potential applications in areas such as bistable frequency lasers and dual femtosecond optical frequency comb is discussed.

Intracavity filtering in SESAM mode-locked fiber lasers: soliton effects and noise performance.

We characterized and analyzed the effect of intracavity spectral filtering in the Er:fiber laser mode-locked with a semiconductor saturable absorber mirror (SESAM). We studied the dispersive properties of bandpass filters and their influence on the characteristics of generated soliton pulses. Our analysis showed that various sideband structures were induced by the filter dispersion profiles and shaped through the interaction of the soliton with the dispersive wave. In addition, intracavity filtering improved the intensity and phase noise of the laser significantly, and we showed optimal filtering conditions for both types of noise. By adding a 10 nm bandpass filter to the laser resonator, the intensity and phase noise were improved 2- and 2.6 times, respectively.

Large energy polarization convertible solitons in an all-PM mode-locked Yb-doped fiber laser system

In this paper, we have demonstrated an all polarization maintaining (PM) composite ultrafast Yb-doped fiber laser system mode-locked by semiconductor saturable absorber mirror (SESAM), which incorporates the amplifier with the resonant cavity together. Benefiting from this composite laser system, not only the pulse energy is significantly improved, but also polarization convertible solitons are realized. When the pump power is lower than 272 mW, the solitons with the central wavelength of 1029.78 nm and the pulse width of 16.54 ps are transmitting along the fast axis. However, the polarization direction of solitons is switched to slow axis as increasing the pump power to be larger than 272 mW. The maximum output power of the solitons can reach 154.93 mW, corresponding to the pulse energy of 9.53 nJ. To the best of our knowledge, this is the first time to realize 90° polarization conversion for ultrafast solitons in an all-PM fiber laser system. We believe the presented approach reveals a pulse scaling and polarization convertible potential of mode-locked fiber laser.

Highly stable passively mode-locked Yb:KGW femtosecond laser at 1041 nm with SESAM

Diode-pumped solid-state laser devices are particularly simple, compact and effective for many specialized applications. The highly stable passively mode-locked Yb:KGd(WO4)2 (Yb:KGW) femtosecond laser is successfully achieved with a semiconductor saturable absorber mirror (SESAM). The laser operated at a center wavelength of 1041.4 nm, and the maximum average output power is 1.11 W. The pulse of 186 fs duration with a single pulse energy of 13.3 nJ and a peak power of 71.5 kW is obtained. The power instability measured at the maximum output power is 0.31 %, indicating that the Yb:KGW laser has excellent power stability.