mW Average Output Power Research Articles

Broad spectral pulse operation of 2 μm Tm:YAP laser based on reflection-type carbon nanotube absorber

We demonstrated the first use of reflection-type single-walled carbon nanotube (RSWCNT) as a saturable absorber in the Q-switched mode-locking (QML) of a diode pumped Tm:YAP operating at 2 μm. The spectrum of the QML laser is centered at 1.97 μm with a broad spectral region of 36 nm. At the incident pump power of 10.33 W, as high as 432 mW average output power was produced in QML laser. The repetition rate of the mode-locked pulse inside the Q-switched envelope was 158 MHz. The dependence of the operational parameters on the pump power was also investigated experimentally.

Single-Frequency Nd:YVO4 Green Laser Using Two Brewster Plate

A pulse laser-diode-array (LDA)-pumped, intracavity frequency-doubled Nd: YVO4 laser has been demonstrated. An birefringent filter consisting of a KTP crystal and two Brewster plates(BP) has been used in the system to realize single-frequency output. Up to 72.4 mW average output power is obtained for 800 mW pumping power with an optical-to-optical conversion efficiency of 9.1%. The maximum peak power of the single-frequency green laser is 22.3 W with the pulse width 162μs.

3.6 µm GaSb-based type-I lasers with quinternary barriers, operating at room temperature

Extension of the room-temperature operation wavelength of GaSb-based type-I laser diodes up to 3.6 µm is presented. Episide-up mounted ridge waveguide lasers with five compressively strained quantum-wells exhibit lasing in pulsed operation with a threshold current densitiy of 862 A/cm2 at infinite resonator length at 15°C and 20 mW of average output power per facet.

10 GHz passive harmonic mode-locking in Er–Yb double-clad fiber laser

In this paper we report passive harmonic mode-locking of an Erbium/Ytterbium-doped double-clad fiber laser with repetition rates up to 10 GHz. The modes synchronization was obtained using Nonlinear Polarization Rotation mechanism. The stable operation at 634th harmonic of the fundamental (15.8 MHz) repetition frequency was achieved. Soliton pulses with the duration of less than 900 fs and 300 mW average output power were obtained.

Femtosecond mode-locked Tm^3+ and Tm^3+-Ho^3+ doped 2 μm glass lasers

We report on the spectroscopic characterization, continuous-wave and continuous wave mode-locked laser performance of bulk Tm(3+):GPNG fluorogermanate and Tm(3+)-Ho(3+):TZN tellurite glass lasers around 2 μm. A slope efficiency of up to 50% and 190 mW of output power were achieved from the Tm(3+):GPNG laser at 1944 nm during continuous wave operation. The Tm(3+)-Ho(3+):TZN laser produced a 26% slope efficiency with a maximum output power of 74 mW at 2012 nm. The Tm(3+):GPNG produced near-transform-limited pulses of 410 fs duration centered at 1997 nm with up to 84 mW of average output power and repetition frequency of 222 MHz when was passively modelocked using an ion-implanted InGaAsSb-based quantum well SESAM. Using the same SESAM, the Tm(3+)-Ho(3+):TZN laser generated 630-fs pulses with 38 mW of average output power at 2012 nm. Data analysis of pulses at different intracavity pulse energies provided an estimation of n(2) at 2012 nm of 2.9 × 10(-15) cm(2)/W for the Tm(3+)-Ho(3+):TZN.

Picosecond diode-pumped 1.5 μm Er,Yb:glass lasers operating at 10–100 GHz repetition rate

Stable ultrafast laser sources at multi-GHz repetition rates are important for various application areas, such as optical sampling, frequency comb metrology, or advanced high-speed return-to-zero telecom systems. We review SESAM-mode-locked Er,Yb:glass lasers operating in the 1.5 μm spectral region at multi-GHz repetition rates, discussing the key improvements that have enabled increasing the repetition rate up to 100 GHz. We also present further improved results with shorter pulse durations from a 100 GHz Er,Yb:glass laser. With an improved SESAM design we achieved 1.1 ps pulses with up to 30 mW average output power. Moreover, we discuss for the first time the importance of beam quality deteriorations arising from frequency-degenerate higher order spatial modes in such lasers.

Generation of 8.5-nJ pulse from all-fiber dispersion compensation-free Yb-doped laser

We report the generation of an 8.5-nJ chirped pulse from a mode-locked all-fiber Yb-doped laser. Mode-locking is achieved through nonlinear polarization evolution (NPE) along with spectral filtering. The laser delivers 135 mW of average output power with positively chirped 10.9-ps pulses. The pulse repetition rate is 15.9 MHz, which results in an energy of 8.5 nJ per pulse. The externally dechirped pulse duration is 223 fs, and the pulse energy is 6 nJ, which corresponds to the peak power of ~27 kW.

Few-cycle oscillator pulse train with constant carrier-envelope- phase and 65 as jitter

We report on an octave-spanning Ti:sapphire laser oscillator stabilized to carrier-envelope-offset frequency zero, generating a pulse train with constant field profile for every pulse. Stabilization is realized using an extended self-referenced locking scheme enabling to lock the carrier envelope-offset phase with less than 65 attosecond rms timing jitter. The stabilized system features a pulse repetition rate of 100 MHz with pulses as short as 4.5 fs and 220 mW average output power. With this laser system it was possible for the first time to demonstrate a spectral interference pattern of 1011 oscillator pulses in an out-of-loop f-to-2f-interferometer.

High-energy soliton pulse generation with a passively mode-locked Er/Yb-doped multifilament-core fiber laser

We report the generation of high-energy short pulses from a mode-locked erbium/ytterbium-doped large-mode-area multifilament-core fiber laser operating in the purely anomalous dispersion regime. The self-starting fiber laser emits 400 mW of average output power at a pulse repetition rate of 44 MHz, corresponding to a pulse energy of 9.1 nJ. The laser produces near transform-limited output pulses with pulse duration of 1.6 ps, corresponding to 5 kW peak power. This new type of low-nonlinearity fibers demonstrates the power and energy scaling potential of fiber-based short pulse lasers in the eye-safe region.

Generation of 25 ps pulses by self induced mode locking of a single broad area diode laser with 300 mW average output power

Detailed investigations of the spatiotemporal and spectral emission properties of a high power diode laser are presented. The AR coated laser diode with design wavelength of 940nm is driven in an external resonator. The laser generates up to 340mW average output power in a train of picosecond pulses with durations of 25ps and repetition rates of 2.6GHz. The mechanism of mode locking is discussed as self pulsation because of the strong correlation between round trip time and repetition rate. The double-sided exponential pulses suggest saturable absorber action.

Fourier domain mode locking at 1050 nm for ultra-high-speed optical coherence tomography of the human retina at 236,000 axial scans per second

A Fourier domain mode-locked (FDML) laser at 1050 nm for ultra-high-speed optical coherence tomography (OCT) imaging of the human retina is demonstrated. Achievable performance, physical limitations, design rules, and scaling principles for FDML operation and component choice in this wavelength range are discussed. The fiber-based FDML laser operates at a sweep rate of 236 kHz over a 63 nm tuning range, with 7 mW average output power. Ultra-high-speed retinal imaging is demonstrated at 236,000 axial scans per second. This represents a speed improvement of approximately10x over typical high-speed OCT systems, paving the way for densely sampled volumetric data sets and new imaging protocols.

Intracavity terahertz-wave generation in a synchronously pumped optical parametric oscillator using quasi-phase-matched GaAs

We generated 1 mW of average output power at 2.8 THz (bandwidth of approximately 300 GHz) in a diffraction-limited beam by placing a 6-mm-long quasi-phase-matched GaAs crystal inside the cavity of a synchronously pumped optical parametric oscillator (OPO). The OPO used type-II-phase-matched periodically poled lithium niobate as a gain medium and was pumped by a mode-locked laser at 1064 nm, with a 7 ps pulse duration, 50 MHz repetition rate, and 10 W average output power. The terahertz radiation was generated by difference frequency mixing between the signal and idler waves of the near-degenerate doubly resonant OPO.

Pulse LDA-pumped single-frequency Nd:YVO 4-KTP green laser using Brewster plate

A pulse laser-diode-array (LDA)-pumped, single-axial-mode, intracavity frequency-doubled Nd:YVO 4 laser has been demonstrated by using an birefringent filter consisting of a KTP crystal and two Brewster plates (BP). Up to 72.4 mW average output power is obtained for 800 mW pumping power with an optical-to-optical conversion efficiency of 9.1%. The maximum peak power of the single-frequency green laser is 22.3 W with the pulse width 162 μs.

All-GaInNAs ultrafast lasers: Material development for emitters and absorbers

Defect engineering is a key feature in material development for active and passive laser devices. Active devices such as surface emitting lasers require excellent material quality with low defect concentration and good strain management. In contrast, passive devices such as saturable absorbers benefit from nonradiative recombination via defect states. Different molecular beam epitaxy (MBE) growth conditions and annealing parameters were developed to optimize GaInNAs for both active and passive devices. We have demonstrated for the first time an all-GaInNAs modelocked vertical external-cavity surface-emitting laser (VECSEL) at 1.3 μm. We combined a GaInNAs VECSEL with a GaInNAs semiconductor saturable absorber mirror (SESAM) in a laser cavity. The VECSEL was optically pumped by an 808 nm semiconductor diode laser. The intracavity GaInNAs SESAM self-starts stable modelocking and generates a pulse duration of 18.7 ps with a pulse repetition rate of 6.1 GHz at 57 mW of average output power at a center wavelength of 1308 nm. In this paper, we briefly review the modelocking result and then focus on the MBE growth and fabrication of both active and passive GaInNAs devices.

Passively mode-locked Nd:GdVO4laser at 912nm

This paper demonstrates the passively mode-locked Nd:GdVO4 laser operating on the 4F3/2–4I9/2 transition at 912 nm by using a semiconductor saturable-absorber mirror for passive mode locking, stable continuous wave mode-locked 912 nm laser was achieved with a repetition rate of 176 MHz. At the incident pump power of 17.7 W, 22.6 mW average output power of stable mode-locked laser was obtained with a slope efficiency of 0.3%.

Simultaneous achievement of narrow pulse width and low pulse-to-pulse timing jitter in 13 μm passively mode-locked quantum-dot lasers

We have analyzed pulse width and timing jitter in passively mode-locked two-section InAs quantum-dot lasers emitting at 1310 nm and have identified two distinct, extensive mode-locked regions with robust short pulses and low timing jitter. A record combination of 2 ps pulses and 25 fs/cycle timing jitter (500 fs, 1-100 MHz), with 1 mW average output power per facet, is demonstrated.

Passively modelocked GaInNAs VECSEL at centre wavelength around 1.3 µm

A passively modelocked GaInNAs vertical-external-cavity surface-emitting laser (VECSEL) is demonstrated for the first time. The VECSEL was optically pumped using an 808 nm semiconductor diode laser. An intracavity GaInNAs semiconductor saturable absorber mirror was used for stable self-starting modelocking and 57 mW of average output power was obtained at a centre wavelength of 1308 nm with a pulse repetition rate of 6.1 GHz and a pulse duration of 18.7 ps.

50-GHz Passively Mode-Locked Surface-Emitting Semiconductor Laser With 100-mW Average Output Power

We have developed a passively mode-locked optically-pumped vertical-external-cavity surface-emitting semiconductor laser (VECSEL) which delivers up to 100 mW of average output power at a repetition rate of 50 GHz in nearly transform-limited 3.3-ps pulses at a wavelength around 960 nm. The high-repetition-rate passive mode locking was achieved with a low-saturation-fluence semiconductor saturable absorber mirror (SESAM) incorporating a single layer of quantum-dots. The output power within a nearly diffraction-limited beam was maximized using a gain structure with a low thermal impedance soldered to a diamond heat spreader. In addition, we systematically optimized the laser resonator to accommodate for the strong thermal lens caused by the optical pumping. We measured the thermal lens dioptric power and present a numerical model which is in good agreement with the measurements and is useful for optimizing resonator designs. The experimental setup is very versatile and its design and construction are discussed in detail

Laser performance of Nd:LaB3O6 cleavage microchips passively Q-switched with a Cr4+:YAG saturable absorber

Passively Q-switched laser oscillation at 1060 nm from an unprocessed Nd:LaB3O6 cleavage microchip with a Cr4+:YAG saturable absorber has been demonstrated. The influence of absorbed pump power, output coupler transmission and cavity length on the output pulse characteristics has been investigated. For a plano-concave cavity with a cavity length of 28 mm, pulse with 100 mW average output power, 4.0 μJ energy, 17 ns duration, 25 kHz repetition rate, and 0.24 kW, peak power was obtained at the absorbed pump power of 1.42 W and output coupler transmission of 3.5%. For a plano-plano cavity with a cavity length of 5 mm, pulse with 85 mW average output power, 2.1 μJ energy, 2.3 ns duration, 40 kHz repetition rate, and 0.89 kW, peak power was obtained at the absorbed pump power of 1.42 W and output coupler transmission of 5.6%. Because a chopper with a 5% duty cycle was employed in the experiments to reduce the influence of pump-induced thermal loading, the above average output powers were obtained at the 5% duty cycle and extrapolated to 100%.

Short-cavity, passively modelocked fibre laser oscillator at 1.5 µm with 550 MHz repetition rate and high average power

A short-cavity fibre laser oscillator emitting 12 ps-long pulses at the fundamental cavity frequency of 550 MHz is reported. The simple, stable and ultra-compact laser cavity consists of a short active fibre section which is spliced to a narrowband fibre Bragg grating, and a butt-coupled semiconductor saturable absorber mirror. Only 8 cm of the heavily Er/Yb co-doped phosphate-glass active fibre is sufficient to produce as much as 775 mW of average output power at 1.5 µm directly from the oscillator.