Picosecond Pulse Generation Research Articles

Characterization of a Pico-Second Phase Conjugate Nd:YVO4 Laser System

We present a full characterization of a pico-second pulse generation from a Nd:YVO4 double-pass amplifier with a phase-conjugate mirror based on a photorefractive BaTiO3 crystal with an external loop geometry. With this system, 7.4 W diffraction-limited pico-second output was generated. A corresponding optical extraction efficiency of >20% was achieved.

Picosecond pulse generation and its simulation in a nonlinear optical mirror mode-locked laser.

A nonlinear mirror composed of a lithium triborate crystal and a dichroic output coupler is used to passively mode lock an Nd:YVO4 laser that is pumped by a diode laser array. A mode-locked output power of 3.2 W, a repetition rate of 178 MHz, a pulse width of 8.4 ps, and a beam quality parameter (M2) of 1.27 are obtained at 1064 nm for a pump power of 10.0 W. The numerical simulation for the steady-state pulse width agrees well with the bandwidth-limited value. A double-pass average gain g(ave) is defined by considering the constancy of the output energy. In the simulation g(ave) is kept as a free parameter, and its value required for the bandwidth-limited pulse is found to be 0.047, whereas its calculated value, based on our definition, is 0.057.

Subharmonic Pulse-Gating in Self-Seeded Laser Diodes for Time- and Wavelength-Interleaved Picosecond Pulse Generation

A new approach of generating high-repetition-rate picosecond pulses at sequentially switching wavelengths has been proposed and experimentally demonstrated. The approach is based on subharmonic pulse-gating and self-seeding of a single Fabry-Perot laser diode. Output of up to ten wavelengths at a repetition rate of 10 GHz has been achieved. The output exhibits a relatively uniform power across the selected wavelengths. The nonlasing modes are being suppressed by more than 20 dB. The maximum timing jitter of an individual wavelength and the ten-wavelength output are measured to be 222 and 181 fs, respectively.

Picosecond pulse generation by internal gain switching in laser diodes

A laser diode structure realizing internal gain switching is suggested for high-power picosecond optical pulse generation. A thin wideband barrier layer is incorporated in the active region of this structure, in order to provide additional control of the carrier distribution and the gain dynamics. The dynamic laser output response to the nanosecond pumping current pulses is modeled and analyzed. The pulse generation mechanism is studied and the possibility to generate optical pulses with power density of 0.416 W/μm2 is demonstrated. This result compares well with that provided by the best modern picosecond laser diodes operating in Q-switching mode.

Compact high-energy picosecond laser for micromachining applications

Picosecond pulse generation by active mode locking and subsequent regenerative amplification in a Nd:vanadate laser crystal has been realized in one and the same cavity using the all-in-one laser concept. An active prelasing stabilization loop has been implemented acting on the mode locker, allowing stable operation up to repetition rates as high as 3 kHz. Sub-30-ps pulses with an energy of 800 μJ have been achieved, constituting the highest peak power and the highest average output power ever demonstrated by means of the all-in-one approach. The combination of compact design, high peak and average power along with a near-diffraction-limited beam profile makes this source a promising tool for precision micromachining applications.

Picosecond pulse generation from passively modelocked vertical cavity diode laser at up to 15 GHz pulse repetition rate

The generation of ultrashort pulses (∼15 ps) from a passively modelocked InGaAs multiple quantum well (MQW) vertical cavity surface emitting diode laser is reported at a repetition rate up to 15 GHz, utilising a cavity configuration that incorporates a reverse-biased quantum well device as a fast saturable absorber. Pulsing at up to 20 GHz rate has been observed on a continuous-wave background.

Picosecond pulse generation with high extinction ratio employing electroabsorption modulator, fibre compressor, and self-phase-modulation-based pulse reshaper

A wavelength-tunable 3.5 ps pulse generator, which employs an electroabsorption modulator (EAM), a fibre pulse compressor, and a self-phase-modulation (SPM)-based pulse reshaper, is developed. An EAM directly generates 21 ps pulses at a repetition rate of 10 GHz, which are compressed to 6 ps by a fibre pulse compressor. An SPM-based pulse reshaper then eliminates the large pedestal of the compressed pulses. Thus, 3.5 ps pulses with extinction ratio larger than 27 dB and timing jitter as small as 150 fs are obtained.

Wide wavelength-switched optical-pulse generation in an L-band mode-locked erbium-doped fiber laser

A simple actively mode-locked erbium-doped fiber-ring laser operating in the L-band for the generation of wavelength-switched picosecond pulses is demonstrated. The conjunction of a polarizer and a polarization controller introduces wavelength-dependent cavity loss, and wavelength switching is achieved by adjustment of the polarization controller. The output wavelength can be switched in a wide range of about 39.2 nm, from 1568.6 to 1607.8 nm. A high-birefringence loop mirror predefines the wavelengths spaced about 0.8-nm apart. During the wavelength-switching process, the modulation frequency of about 2.5 GHz remains unchanged and the pulse-width is less than 56 ps for each wavelength. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 196–199, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20585

Impact-ionization wave breakdown and generation of picosecond pulses in the ultrahigh-frequency band in GaAs drift step-recovery diodes

It is shown experimentally for the first time that the operation of GaAs drift step-recovery diodes produced on the basis of p + - p 0 - n 0 - n + is accompanied by the generation of ultrahigh-frequency oscillations in the form of trains of short pulses with a duration of ~10 ps. The amplitude and repetition frequency of these pulses are as high as ~100 V and ~(10-100) GHz, respectively. The phenomena of delayed reversible wave breakdown and excitation of ultrahigh-frequency oscillations in the structures of GaAs step-recovery diodes are found to open up new avenues for progress both in the physics and technology of semiconductor devices based on GaAs structures and in the technology of ultrahigh-frequency systems and devices that deal with pulsed sig- nals of picosecond-scale duration. © 2003 MAIK "Nauka/Interperiodica".

Picosecond high-voltage drift diodes based on gallium arsenide

Experimental results of studying the dynamics of recovery of diodes based on lightly doped epitaxial layers of gallium arsenide are reported. The diodes under consideration belong to the class of drift diodes with step recovery and are designed to operate in circuits for shaping and generating picosecond pulses. The obtained values of the reverse-voltage recovery rate (dU/dt≈2000 V/ns) far exceed the published ultimate recovery rates for picosecond-response diodes with charge accumulation and are unprecedentedly high for step-recovery drift diodes.

Broadband nonlinear optical conversion of a high-energy diode-pumped picosecond laser

We report on a high-energy picosecond pulse generation out made of a simple and inexpensive all-solid-state diode-pumped oscillator. The system produces 200 nJ, 7-ps pulses with an average power as high as 3 W, using laser components with a total price of all opto-mechanical components of about $10,000. High-power broadband continuum generation is demonstrated in a specially selected single mode GeO 2-doped fiber.

Generation of dual-wavelength picosecond pulses with close wavelength separation from a self-seeded Fabry-Perot laser diode

We present a simple and low-cost technique for the generation of dual-wavelength picosecond laser pulses with a close wavelength separation. The technique is based on the selection of two close wavelengths from one of the modes of a self-seeded Fabry-Perot laser diode (FP-LD) with a fiber Bragg grating (FBG) that has a slightly split reflection spectrum. With this technique, the intensities of the pulses at the two wavelengths can be equalized by adjusting the temperature of the FP-LD, and the wavelength separation can be changed continuously without changing the repetition rate of the output pulses by tuning the separation of the reflection peaks of the FBG. Generation of stable dual-wavelength pulses with a pulsewidth of 36.0-50.0 ps and a tunable wavelength separation from 0.21 to 0.44 nm at a pulse rate of 2 GHz was demonstrated.

Near-infrared continuum generation of femtosecond and picosecond pulses in doped optical fibers

We report broad continuum generation in GeO2-doped silica fibers induced by femtosecond and picosecond pulses generated by novel high-power laser sources. Over 0.5 W of average power in a broad-band picosecond continuum is generated in the near-infrared part of the spectrum from 800 to 1500 nm.

Generation and wavelength switching of picosecond pulses by optically modulating a semiconductor optical amplifier in a fiber laser with optical delay line

A novel actively mode-locked fiber laser having a semiconductor optical amplifier playing the roles of both a gain element and an optically controlled mode-locker and eight cascaded fiber Bragg gratings playing the role of the wavelength selecting element is proposed and demonstrated. Stable amplitude equalized pulse trains with a pulsewidth about 43 ps at 2.5 GHz have been obtained by injecting optical control signals into the laser. Wavelength switching among eight wavelengths is achieved by merely tuning an intracavity optical delay line. This all-optical generation and wavelength-switching scheme should be useful in applications where picosecond pulse trains at high repetition rates are desired.

Picosecond pulse generation with 1.5 µm passively modelocked surface-emitting semiconductor laser

The authors report the first demonstration of an optically pumped passively modelocked surface-emitting semiconductor laser operating in the 1.5 µm region. The modelocked laser emits pulses of 6.5 ps full width at half maximum duration with an average power of 13.5 mW at a fundamental repetition rate of 1.342 GHz. The peak power was 1.6 W.

Picosecond acoustic phonon pulse generation in nickel and chromium

The generation mechanisms for picosecond acoustic phonon pulses excited by ultrashort optical pulses in metals with strong electron-phonon coupling are elucidated. By means of an interferometric probing technique to extract changes in optical phase and amplitude, the acoustic pulse shapes in the transition metals Ni and Cr are shown to be governed by both thermal and nonequilibrium electron diffusion. Quantitative comparison of the results with a model that takes into account the nonequilibrium electron dynamics and ultrasonic attenuation gives excellent agreement.

Smoothly wavelength-tunable picosecond pulse generation using a harmonically mode-locked fiber ring laser

A simple design of a stable, smoothly wavelength-tunable picosecond pulse generator has been demonstrated using a dispersion-tuned, harmonically mode-locked fiber ring laser with a directly modulated semiconductor optical amplifier (SOA). The SOA functions as both a polarization-insensitive mode locker and a supermode noise suppressor. Near-linearly chirped pulses are generated and compressed to less than 4 ps when the intracavity dispersion is anomalous while 11-ps, near-transform-limited pulses are generated without compression when the dispersion is normal. Smooth wavelength tuning is achieved over more than 11 nm by only tuning the modulation frequency and pulse characteristics are stable over the entire tuning span. A simple numerical model successively simulates the operation principle of the system. The tuning range is determined by both the gain profile and the total intracavity dispersion. The dispersion and the SOA ensure the long-term stability of the system.

Dispersion-flattened-fibre optical parametric oscillator for wideband wavelength-tunable ps pulse generation

A scheme of a fibre-optic parametric oscillator for picosecond pulse generation with wide wavelength-tunability is proposed on the basis of a dispersion-flattened-fibre gain medium and is indeed implemented with either of 1415–1505 or 1600–1750 nm operation wavelength ranges and 6–400 pJ pulse energy.

Addendum to: Picosecond pulse generation for visible semiconductor laser operating at 650‐NM wavelength with the use of the gain‐switching technique

AbstractOriginally published Microwave Opt Technol Lett 35: 65–67, 2002. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 342–342, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10584

Passively Q-switched operation of a double contact tapered InGaAs/GaAs diode laser

High power picosecond pulse generation from a two-contact tapered two quantum well 980 nm InGaAs/GaAs diode laser is investigated using a passive Q-switching technique for the first time. Tail-free and single peak Q-switched pulses are obtained by applying reverse bias voltages in the range of 0 to −9 V to the absorber section of the device. Optical pulses with 41 ps (down to 29 ps) durations and peak powers in excess of 1.5 W are obtained in a well-defined single lobed far-field. Such an improvement in the optical pulses is attributed to a reduction of absorber recovery time.