Semiconductor Saturable Absorber Mirror Research Articles

High-speed two-photon polymerization 3D printing with a microchip laser at its fundamental wavelength.

High-resolution, high-speed 3D printing by two-photon polymerization (2PP) with a Nd:YVO4 Q-switched microchip laser at its fundamental wavelength of 1064 nm is demonstrated. Polymerization scan speeds of up to 20 mm/s and feature sizes of 250 nm are achieved using a high repetition rate Q-switched microchip laser with a semiconductor saturable absorber mirror (SESAM) and photoresist with a new photo-initiator bearing 6-dialkylaminobenzufuran as electron donor and indene-1,3-dione moiety as electron acceptor. The obtained results demonstrate the high potential of Q-switched microchip lasers for applications in 2PP 3D printing.

Mode-locked femtosecond laser with a rotary Nd:glass disk.

We demonstrate here femtosecond pulses output from a rotary Nd:glass disk laser, mode-locked with semiconductor saturable absorber mirrors. We obtained an average output power of 0.66W in cw operation and an average output power of 0.49W with a duration of 324fs in mode-locked operation in the case of an absorbed pump power of 7.3W. To the best of our knowledge, it is the first time that sub-picosecond pulses have been obtained from rotary Nd:glass disk lasers. It shows a new concept for all-solid-state mode-locked glass lasers with high power.

10.3 W diode-pumped passively mode-locked Nd:YAG laser at 1319 nm with a semiconductor saturable absorber mirror

A high-power diode-end-pumped continuous-wave (CW) passively mode-locked picosecond (ps) 1319 nm Nd:YAG laser was demonstrated with a semiconductor saturable absorber mirror (SESAM). The oscillator cavity was accurately designed to optimize the laser beam radii in the centre of crystal and on the SESAM. At an absorbed pump power of 102 W, the maximum mode-locked output power of 10.3 W was achieved with pulse width of 27.1 ps and a beam quality factor M2 = 1.38 at the repetition rate of 76 MHz, corresponding to an optical-optical efficiency of 10.1%. To the best of our knowledge, this is the first demonstration of diode-pumped passively CW mode-locked ps Nd:YAG laser at 1319 nm with a SESAM.

Switchable Dual-Wavelength Mode-Locked Fiber Laser Source for In-PCF Parametric Frequency Conversion Applied to CARS Microscopy

A self-started, switchable dual-wavelength all-polarization-maintaining mode-locked (ML) fiber laser for optical parametric generation (OPG) in photonic crystal fiber (PCF) applied to coherent anti-stokes Raman scattering (CARS) microscopy is reported in this paper. The complete laser setup is built in an all-fiber structure composed of commercial elements. It is based on a linear cavity with an active medium—namely, Ytterbium-doped fiber (YDF), a pair of fiber Bragg gratings as switchable partial mirrors between 1031.5 and 1049.7 nm, and a semiconductor saturable absorber mirror functioning also as the mode-locking device. The seed laser is amplified to 650 mW average power by two YDF amplifiers. The source delivers a pulse-train output of 30.9 ps at 1031.5 ps and 31.6 ps at 1049.7, a 3.1-MHz repetition rate, and over 200 nJ pulse energy and 6 kW of peak power at fundamental ML operation. The properties of this switchable dual-wavelength source ensures the correct OPG by degenerated four-wave mixing in PCF fulfilling the phase matching condition which corresponds to CARS resonance of 2850 $ {\mathbf{c}}{ {\mathbf{m}}^{ - 1}}$ (CH3-O molecular bonds) at 1031.5 nm and 1475 $ {\mathbf{c}}{ {\mathbf{m}}^{ - 1}}$ (CH2 δ molecular bonds) at 1049.7 nm.

InAs/GaAs quantum dot semiconductor saturable absorber for controllable dual-wavelength passively Q-switched fiber laser

We experimentally demonstrate the first use of 1550-nm InAs/GaAs quantum dot semiconductor saturable absorber mirror (QD-SESAM) in the dual-wavelength passively Q-switched (QS) erbium doped fiber (EDF) laser. The dual-wavelength QS lasing was obtained at a pump threshold of 180 mW with the average output power of 2.2 mW and the spacing between the two lasing wavelengths is 14 nm. A large absorption ranging from 1520 to 1590 nm has been realized when no substrate rotation was employed during the molecular beam epitaxy growth of the QD-SESAM indicating the potential to generate a 60 nm spacing of the dual-wavelength QS lasing peaks by changing the positions in the QD-SESAM and replacing EDF by co-doped fiber as gain medium. These results have provided a new opportunity towards achieving the stable and wide wavelength-tunable dual-modes fiber lasers.

Broadly Tunable and Passively Mode-Locked Operations of Yb3+,Gd3+:SrF2 Laser

Both tunable and passively mode-locked laser oscillators based on an efficient Yb,Gd:SrF2 crystal are reported for the first time. Charge compensation ions of Gd3+ enhanced the emission and absorption cross section of Yb,Gd:SrF2 crystal markedly. With the aid of birefringent filter, a 61.1-nm continuous-wavelength-tunable laser from 1020.2 to 1081.3 nm was obtained, making it a potential candidate for ultrafast lasers. Based on a semiconductor saturable absorber mirror, a diode-pumped passively mode-locked laser with the pulse width of 951 fs was realized. The oscillator operated at a repetition rate of 92 MHz.

Wavelength-tunable passively mode-locked all-fiber laser at 1.5 μm.

We have experimentally demonstrated a wavelength-tunable passively mode-locked all-fiber laser at 1.5 μm wavelength by using an erbium-doped fiber amplifier, a fiber-pigtailed semiconductor saturable absorber mirror, and a tunable birefringence Sagnac filter. In our work, by properly setting the polarization state of the propagating light in the birefringence Sagnac filter, the mode-locked lasing wavelength can be continuously tuned from 1544.1 to 1560.8 nm, corresponding to a tuning range of 16.7 nm. At a central wavelength of 1548.5 nm, the fiber laser delivers pulses as short as 713.2 fs with a repetition rate of 4.65 MHz, a 3 dB bandwidth of 5.7 nm, and an average output power of 4.86 mW. Our results show that such a mode-locked all-fiber laser has great potential in applications in nonlinear optics at the 1.5 μm band.

Efficient 1 µm Laser Emission of Czochralski-Grown Nd:LGSB Single Crystal.

A 5.0-at.% Nd-doped La0.64Gd0.41Sc2.95(BO3)4 (Nd:LGSB) borate laser crystal was successfully grown by the Czochralski method, for the first time to our knowledge. The spectroscopic properties of the grown crystal are discussed and 1 µm laser emission, under end-pumping with a fiber-coupled diode laser at 807 nm, is reported. A c-cut Nd:LGSB medium yielded 1.35 W continuous-wave output power at 0.63 overall optical-to-optical efficiency, with respect to the absorbed pump power, together with the high 0.68 slope efficiency. With an a-cut Nd:LGSB sample, 0.81 W output power at 0.52 optical-to-optical efficiency was obtained. The laser emission performances under quasi-continuous wave pumping are presented as well, for both c-cut and a-cut crystals. Passive Q-switching was investigated with a semiconductor saturable absorber mirror (SESAM). Laser pulses with 2.2 µJ energy and 32.8 ns durations were recorded from a-cut Nd:LGSB. The average output power reached 0.36 W at 1.55 W absorbed pump power. Passive mode-locking with SESAM was achieved in a long Z-type resonator. Ultrashort pulses with 0.19 W average power, 1.63 nJ energy, and 1.43 ps pulse duration, at 118 MHz repetition rate, are demonstrated for the a-cut Nd:LGSB medium.

Mode and Wavelength-Switchable Pulsed Fiber Laser With Few-Mode Fiber Grating

We propose and demonstrate a mode and wavelength-switchable pulsed fiber laser using two-mode fiber Bragg grating (TM-FBG) as both transverse mode converter and wavelength selector. The mode-locking mechanism is based on saturable absorption of semiconductor saturable absorption mirror (SESAM). Due to the use of low polarization-dependent mode-locking method, polarization disturbation between mode-locking and transverse-mode selection has been effectively eliminated, thus enabling flexible transverse-mode selection with simultaneous mode-locking operation. Moreover, through the optimized offset launching technique, this laser can operate at the wavelengths of the fundamental mode (LP01) and second-order mode (LP11), and thus export cylindrical vector beams (CVBs) and fundamental mode beams at the TM-FBG output port, respectively. This all-fiber laser is a simple, low-cost, and flexible source for mode-division multiplexing system and other applications.

Q-switched mode-locked ytterbium-doped fiber laser with radial polarization

A Q-switched mode-locked, radially polarized ytterbium-doped fiber laser was demonstrated. In the study, the combination of a c-cut YVO4 birefringent crystal and a single-lens was utilized as the intracavity polarization discriminator, and a semiconductor saturable absorber mirror was used as passive mode-locked element. A narrow band-pass filter was inserted into the cavity to stabilize the mode-locked pulses and lasing wavelength. At the absorbed pump power of 1.56 W, the output power was 202 mW, corresponding to slope efficiency of 22.8%. The repetition rate and width for Q-switched envelope were 60.5 kHz and 315 ns, respectively. The mode-locked pulses inside the Q-switched envelope had a repetition rate of 66.67 MHz, the pulse width of 163 ps and the largest single-pulse peak power of 975 W.

Design and analysis of passively mode-locked all-quantum-dot electrically-driven VECSEL

Detailed characteristics of newly proposed passively mode-locked vertical-external-cavity surface-emitting laser (VECSEL) are investigated. The active material is a quantum dot (QD) InAs/GaAs lasing at a wavelength of 1.3μm. The QD-VECSEL is electrically-driven and is mode-locked by p-i-n QD based semiconductor saturable absorber mirror (SESAM). Time-domain travelling-wave models together with carrier concentration rate equations are employed for investigating the operation of the device. Different parameters that affect the mode-locking performance of the proposed device are examined. Such parameters include the VECSEL to SESAM beam area ratio, the reverse voltage applied to the p-i-n QD-SESAM, the injected current to the VECSEL, and the QD inhomogeneous broadening. The gain, absorption and pulse dynamics are studied, along with the spectral characteristics of the pulse train. The obtained results show that there is a possibility of obtaining mode-locked laser pulses from that device at a wavelength of 1.3μm with pulse repetition frequency of 45 GHz and average pulse width of approximately 10 ps.

High power diode-pumped passively mode-locked Nd:YVO4 laser at repetition rate of 3.2 GHz**Project supported by the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB16030200), the National Natural Science Foundation of China (Grant Nos. 11774410 and 61575217), the National Key Scientific Instruments Development Program of China (Grant No. 2012YQ120047), and the Key Research Program of Frontier Sciences

A compact high power diode-pumped passively mode-locked Nd:YVO4 laser with high repetition rate is realized. Using an Nd:YVO4 crystal and a semiconductor saturable absorber mirror (SESAM) in the oscillator, the picosecond pulse output with an average power of 1.38 W, a repetition rate of 3.24 GHz, and a pulse duration of 11.4 ps is achieved. After one stage of amplification, the final output power reaches 11.34 W, corresponding to a total optical-to-optical efficiency of about 32%. The root mean square (RMS) value of power fluctuation is demonstrated to be less than 0.6% in 24 hours, showing a superior stability with the compact configuration.

Rogue waves in a linear cavity Yb-fiber laser through spectral filtering induced pulse instability.

In this Letter, experimental observation of dissipative rogue waves (DRWs) due to spectral filtering induced pulse instabilities in a mode-locked ytterbium (Yb) fiber laser has been presented. A semiconductor saturable absorber mirror was used to mode-lock the linear cavity laser and a chirped fiber Bragg grating (CFBG) was used for dispersion management, which also acted as a spectral filter and output coupler. Under stable conditions, the cavity delivered dispersion managed dissipative solitons of 447fs duration and 0.69nJ pulse energy at 10.19MHz repetition rate with uniform intensity distribution over a long time span. As the spectral width increased with pump power, random intensity fluctuations were observed in the pulse train due to the filtering effect of the CFBG. Employing a dispersive Fourier transform by stretching the output pulse train in time allowed the existence of DRWs more than 4 times stronger than the significant wave height to be observed. Further increments of pump power led to a stable multi-pulsing state.

Effect of SESAM on continuous-wave multi-wavelength fiber ring-cavity laser with semiconductor optical amplifier

The effect of semiconductor saturable absorber mirror (SESAM) on continuous-wave multi-wavelength fiber ring-cavity laser with semiconductor optical amplifier (SOA) is experimentally demonstrated. The evolutionary process of multi-wavelength oscillation and the decrease of oscillating mode number caused by an SESAM are discussed. It’s found that the free oscillating mode number of the multi-wavelength fiber ring-cavity laser with SOA can be upto three, and the lasing wavelengths are 1573.8 nm, 1578.09 nm and 1582.37 nm, respectively. When a SESAM is inserted in the fiber ring-cavity, it narrows the amplified spontaneous emission (ASE) spectrum of the SOA, and the oscillating mode number of the multi-wavelength fiber ring-cavity lasers with SOA decreases to two, a stable dual-wavelength lasing at 1560.91 nm and 1564.12 nm is obtained.

Focus on lasers, imaging, and microscopy

Focus on lasers, imaging, and microscopy

7.6-W diode-pumped femtosecond Yb:KGW laser**Project supported by the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB16030200), the National Natural Science Foundation of China (Grant Nos. 11774410, 61575217, and 61675158), the National Key Scientific Instruments Development Program of China (Grant No. 2012YQ120047), and the Key Research Program of Frontier Sciences of Chinese Academy of Sciences (Grant No.

We have demonstrated a high power diode-pumped mode-locked femtosecond Yb:KGW laser with semiconductor saturable absorber mirror (SESAM). By using an output coupler with 10% transmittance, the laser delivered 160-fs pulses with average output power of 7.6 W at a repetition rate of 78 MHz, corresponding to pulse energy of 97 nJ and peak power of 606 kW.

Investigation of the reabsorption effect in an all-fiberized mode-locked thulium-doped fibre laser

We investigate the influence of the reabsorption effect on pulse characteristics in an all-fiberized ultra-fast thulium-doped fibre laser system. Mode-locked operation was enabled by a semiconductor saturable absorber mirror, and the laser generated stable ultra-short pulses at a repetition rate of 11.29 MHz. By changing the length of the thulium-doped fibre, and hence the reabsorption loss, we found that the reabsorption effect had a significant influence on the optical spectrum and pulse duration of the mode-locked fibre laser. Output durations from 2.04 ps to 20.8 ps have been achieved, corresponding to operating wavelengths changing from 1968.9 nm to 2054.7 nm. Qualitative explanations of these phenomena have also been demonstrated.

Diode-Pumped Passively Mode-Locked YVO4/Nd:YVO4 Composite Crystal Laser

We report on a passively mode-locked YVO4/Nd:YVO4 composite crystal laser using a semiconductor saturable absorber mirror. At a pump power of 21.39 W, we achieve a 3.51 W average output power from a continuous wave mode-locked laser with a repetition rate of passively mode-locked pulse of 89 MHz and a pulse width of 38.3 ps. The pulse energy and peak power are 39.4 nJ and 1.03 kW, respectively. Our experiment results show that a composite crystal is an excellent laser crystal for mode locking.

Study of dielectric coatings for broadband operation of surface-emitting semiconductor lasers

We investigate antireflection (AR) coating materials for two different operation lasing regimes requiring broad spectral bandwidth. We characterize high-power continuous-wave (CW) wavelength-tunable vertical-external-cavity surface-emitting semiconductor lasers and their passive mode-locking capabilities when using semiconductor saturable absorber mirrors. One laser gain design was investigated with different single dielectric layers as AR coatings. The dielectric coating materials used were SiO2, Al2O3, Ta2O5, and TiO2. The AR coating was designed to reduce pump reflection and increase the confinement factor of the microcavity. Average power of 4.6 W in CW and a total wavelength tuning range of 42 nm has been observed with the SiO2-coated structure. The shortest pulse of 708 fs was also observed for the SiO2-coated structure, with a corresponding CW wavelength tuning range of 36 nm.

Passive harmonic mode-locked ytterbium-doped fiber laser with chirped pulse amplification

A passive harmonic mode-locked ytterbium-doped fiber laser with all-normal dispersion has been demonstrated. The mode-locking mechanism of the laser is based on the interaction between semiconductor saturable absorber mirror and nonlinear polarization rotation. The repetition rate of the laser is adjustable from 7.91 MHz to 31.65 MHz. Via the chirped pulse amplification, the 1 ps mode-locked pulse at the fundamental repetition rate of 7.91 MHz is compressed to 720 fs with single pulse energy of 12.6 nJ.