Picosecond Optical Pulses Research Articles

Laser diode structures with a saturable absorber for high-energy picosecond optical pulse generation by combined gain-and Q-switching

The performance of gain-switched Fabry–Perot asymmetric-waveguide semiconductor lasers with a large equivalent spot size and an intracavity saturable absorber was investigated experimentally and theoretically. The laser with a short (∼20 μm) absorber emitted high-energy afterpulse-free optical pulses in a broad range of injection current pulse amplitudes; optical pulses with a peak power of about 35 W and a duration of about 80 ps at half maximum were achieved with a current pulse with an amplitude of just 8 A and a duration of 1.5 ns. Good quality pulsations were observed in a broad range of elevated temperatures. The introduction of a substantially longer absorber section leads to strong spectral broadening of the output without a significant improvement to pulse energy and peak power.

Monolithically integrated tunable mode-locked laser diode source with individual pulse selection and post-amplification.

We report the generation of high-peak-power picosecond optical pulses in the 1.55 μm spectral band from a monolithically mode-locked laser integrated with a pulse selector and power booster. High-peak-power (>1 W) pulses with durations of 15.4 ps at a 55 MHz selected rate are demonstrated, indicating that this device shows promise as a high-peak-power pulsed light source for bio-photonic applications.

Wideband slow-light propagation with no distortion in a nanofiber-plane-grating composite waveguide

A nanofiber-plane-grating composite slow-light waveguide to achieve wideband slowlight propagation with no distortion is proposed. The waveguide is formed by embedding a tapered nanofiber into a V-groove on a plane-grating surface. By optimizing the waveguide structural parameters, a slow-light effect with bandwidth of about 1453 GHz is obtained. Based on finite-difference time-domain (FDTD) method, we analyze the waveguide’s optical properties and slow-light characteristics. Simulation results show that a picosecond optical pulse propagating in the slow-light waveguide can be delayed for about 980 fs and without distortion. The group velocity of the optical pulse can be reduced to about 0.3c (c is the speed of light in vacuum). This study will provide important theoretical basis and innovative ideas for the development of new-type slow-light elements.

Freely Triggerable Picosecond Pulses From a DBR Ridge Waveguide Diode Laser Near 1120 nm

In this letter, we present results on the pulsed operation of a distributed Bragg reflector ridge waveguide diode laser with wavelength close to 1120 nm. Picosecond optical pulses were generated by gain-switching at variable repetition frequencies up to 80 MHz. In single-pulse operation, a pulse width of 92 ps with a pulse peak power of 1.7 W at 10 MHz could be obtained. Investigations in operation at higher injection current pulse amplitude increased the pulse peak power to 2.6 W, but also showed significant trailing pulses which is typical for gain-switched diode lasers. The shape of the pulses is stable over the whole range of the investigated repetition frequencies from 5 to 80 MHz. At an operation temperature of 25 °C, the emitted radiation has a wavelength of 1114.7 nm and increases to 1116.4 nm at 45 °C. The central wavelength does not change significantly at higher output power.

Widely Continuous Tunable ps Pulse Train Generation Based on SOA Nonlinear Dynamics

We propose a simple setup based on nonlinear dynamics in a semiconductor optical amplifier (SOA) and solitonic compression for the generation of stable and tunable repetition rate picosecond (ps) optical pulses. A quantum-well SOA is used to amplify electrical-optic-modulated rectangular optical signal, during which the nonlinear amplification process induces front-edge distortion. Due to the non-zero linewidth enhancement factor, the front-edge distortion can be isolated by the optical filtration of the chirped frequency component, which eventually becomes Gaussian-like pulse train of tens of ps FWHM pulsewidth. Following a stage of solitonic compression and a stage of pedestal suppression, we are able to obtain a train of 1-ps high-quality pulses for which the root mean square timing jitter is $C$ -band.

Ultrafast High-Repetition-Rate Waveguide Lasers

We report on progress in the field of integrated mode-locked waveguide lasers with an emphasis on compact monolithic designs producing picosecond and femtosecond optical pulses at multi-GHz repetition rates.

Picosecond optical vortex pulse illumination forms a monocrystalline silicon needle.

The formation of a monocrystalline silicon needle by picosecond optical vortex pulse illumination was demonstrated for the first time in this study. The dynamics of this silicon needle formation was further revealed by employing an ultrahigh-speed camera. The melted silicon was collected through picosecond pulse deposition to the dark core of the optical vortex, forming the silicon needle on a submicrosecond time scale. The needle was composed of monocrystalline silicon with the same lattice index (100) as that of the silicon substrate, and had a height of approximately 14 μm and a thickness of approximately 3 μm. Overlaid vortex pulses allowed the needle to be shaped with a height of approximately 40 μm without any changes to the crystalline properties. Such a monocrystalline silicon needle can be applied to devices in many fields, such as core–shell structures for silicon photonics and photovoltaic devices as well as nano- or microelectromechanical systems.

Study of the Planacon XP85012 photomultiplier characteristics for its use in a Cherenkov detector

Main properties of the multi-anode microchannel plate photomultiplier to be used in a Cherenkov detector are discussed. The laboratory test results obtained using irradiation of the MCP-PMT photocathode by picosecond optical laser pulses with different intensities (from single photon regime to the PMT saturation conditions) are presented.

Lax Pair, Conservation Laws, Solitons, and Rogue Waves for a Generalised Nonlinear Schrödinger–Maxwell–Bloch System under the Nonlinear Tunneling Effect for an Inhomogeneous Erbium-Doped Silica Fibre

AbstractUnder investigation in this article is a generalised nonlinear Schrödinger-Maxwell-Bloch system for the picosecond optical pulse propagation in an inhomogeneous erbium-doped silica optical fibre. Lax pair, conservation laws, Darboux transformation, and generalised Darboux transformation for the system are constructed; with the one- and two-soliton solutions, the first- and second-order rogue waves given. Soliton propagation is discussed. Nonlinear tunneling effect on the solitons and rogue waves are investigated. We find that (i) the detuning of the atomic transition frequency from the optical pulse frequency affects the velocity of the pulse when the detuning is small, (ii) nonlinear tunneling effect does not affect the energy redistribution of the soliton interaction, (iii) dispersion barrier/well has an effect on the soliton velocity, whereas nonlinear well/barrier does not, (iv) nonlinear well/barrier could amplify/compress the solitons or rogue waves in a smoother manner than the dispersion barrier/well, and (v) dispersion barrier could “attract” the nearby rogue waves, whereas the dispersion well has a repulsive effect on them.

Generation of a 2.2 nJ picosecond optical pulse with blue-violet wavelength using a GaInN master oscillator power amplifier

We report the generation of a picosecond optical pulse with 2.2 nJ pulse energy at blue-violet wavelengths using a GaN-based mode-locked laser diode (MLLD) and a semiconductor optical amplifier (SOA). The picosecond optical pulse generated by MLLD at a frequency of 812 MHz was amplified effectively by SOA. We optimized SOA with a widely flared waveguide structure to generate a high optical pulse energy.

Multiwavelength 25-GHz picosecond pulse generation with phase modulation and double-side Mamyshev reshaping.

We demonstrate a simple, robust, and cost-effective method of generating high-speed multiwavelength picosecond optical pulses. This method is based on chirp compression of phase-modulated light, followed by nonlinear pulse compression and reshaping with a double-side Mamyshev reshaper. We show that this method becomes power efficient when the repetition rate is increased to 25GHz. Wavelength-tunable optical pulses with a repetition rate of 25GHz and pulse width of ∼2 ps, which can be temporally multiplexed to 100GHz, are experimentally obtained over a large spectral range with moderate electrical and optical power. Simultaneous pulse generation on four wavelengths is demonstrated.

Strongly asymmetric waveguide laser diodes for high brightness picosecond optical pulses generation by gain switching at GHz repetition rates

Rate equations analysis, supported by travelling wave simulations, is used to show that a diode laser design with a very low (<1%) confinement factor is optimal for generating streams of high energy optical pulses for nonlinear applications by large-signal modulation with both existing and potentially improved ac current generators. An asymmetric waveguide laser design is proposed to realize this low confinement factor while simultaneously maintaining good beam properties in a single transverse mode. The rate equations model complemented by transport equations is used to quantify the effects of transport in the broad optical confinement layer(s) on the laser dynamics, and it is shown that in the proposed laser construction the detrimental effects of transport are weak.

Nonlinear optical response of low loss silicon germanium waveguides in the mid-infrared.

We have investigated the nonlinear optical response of low loss Si(0.6)Ge(0.4) / Si waveguides in the mid-infrared wavelength range from 3.25- 4.75μm using picosecond optical pulses. We observed and measured the three and four-photon absorption coefficients as well as the Kerr nonlinear refractive index. The dynamics of the spectral broadening suggests that, in addition to multiphoton absorption, the corresponding higher order nonlinear refractive phenomena also needs to be included when high optical pulse intensities are used at mid-infrared wavelengths in this material.

Lossless fractional repetition-rate multiplication of optical pulse trains.

We propose and experimentally demonstrate repetition-rate multiplication of picosecond optical pulse trains by a fractional factor based on temporal self-imaging, involving temporal phase modulation and first-order dispersion. Multiplication factors of 1.25, 1.33, 1.5, 1.6, 1.75, 2.25, 2.33, and 2.5 are achieved with high fidelity from a mode-locked laser with an input repetition-rate between 10 and 20GHz.

Deep-red semiconductor monolithic mode-locked lasers

A deep-red semiconductor monolithic mode-locked laser is demonstrated. Multi-section laser diodes based on an AlGaAs multi-quantum-well structure were passively mode-locked, enabling the generation of picosecond optical pulses at 752 nm, at pulse repetition rates of 19.37 GHz. An investigation of the dependence of the pulse duration as a function of reverse bias revealed a predominantly exponential decay trend of the pulse duration, varying from 10.5 ps down to 3.5 ps, which can be associated with the concomitant reduction of absorption recovery time with increasing applied field. A 30-MHz-tunability of the pulse repetition rate with bias conditions is also reported. The demonstration of such a compact, efficient and versatile ultrafast laser in this spectral region paves the way for its deployment in a wide range of applications such as biomedical microscopy, pulsed terahertz generation as well as microwave and millimeter-wave generation, with further impact on sensing, imaging and optical communications.

Light source design using Kagome-lattice hollow core photonic crystal fibers

Supercontinuum (SC) light source is designed using high pressure Xe-filled hollow core Kagome-lattice photonic crystal fiber. Using finite element method with perfectly matched layer, SC spectra in normal chromatic dispersion region have been generated using picosecond optical pulses from relatively less expensive laser sources.

Monolithically integrated selectable repetition-rate laser diode source of picosecond optical pulses.

We describe the characterization of a monolithically integrated photonic device for short pulse generation featuring a mode-locked laser diode, a Mach-Zehnder modulator (MZM), and a semiconductor optical amplifier (SOA). The integrated device is designed for fabrication by a generic foundry scheme with a view to ease of design, testing, and manufacture. Trains of 6.8 ps pulses are generated at repetition rates that are electronically switchable from 14 GHz to 109 MHz. The SOA boosts the peak power by 7.4 dB, and the pulses are compressible to 2.4 ps by dispersion compensation using single-mode telecommunications fiber.

PICOSECOND OPTICAL PULSE GENERATION USING CASCADED MACH-ZEHNDER ELECTRO-OPTIC LIGHT INTENSITY MODULATORS

In this paper, the author proposes a technique for the generation of picosecond optical pulses using cascaded Mach-Zehnder electrooptic light intensity modulators. Each individual Mach-Zehnder modulator is driven by the same microwave signal. By providing proper dc bias to the modulators, the repetition frequency of the generated optical pulse can be made equal to twice the frequency of the applied microwave drive signal. By tuning the microwave drive frequency, the repetition frequency of the generated optical pulse can be varied. The normalized optical pulse intensity and pulse width of the generated pulse have been calculated. The variation of the pulse width with different system parameters is also presented. Typical pulse width of 2.52 picosecond can be achieved using a cascade of four modulators driven by 60 GHz mm-wave signal.

7-ps optical pulse generation from a 1064-nm gain-switched laser diode and its application for two-photon microscopy

In this study, we investigated the picosecond optical pulse generation from a 1064-nm distributed feedback laser diode under strong gain switching. The spectrum of the generated optical pulses was manipulated in two different ways: (i) by extracting the short-wavelength components of the optical pulse spectrum and (ii) by compensating for spectral chirping in the extracted mid-spectral region. Both of these methods shortened the optical pulse duration to approximately 7 ps. These optical pulses were amplified to over 20-kW peak power for two-photon microscopy. We obtained clear two-photon images of neurons in a fixed brain slice of H-line mouse expressing enhanced yellow fluorescent protein. Furthermore, a successful experiment was also confirmed for in vivo deep region H-line mouse brain neuron imaging.

Microchip Laser-Based Optoelectronic System for Kilovolt Picosecond Electromagnetic Pulse Generation

An optoelectronic electromagnetic generator was developed for the creation and shaping of picosecond pulses. The system integrated a homemade compact picosecond source. The infrared pulse-source switches optoelectronic components mounted on a microstrip line generator. The technology is based on a microchip laser that delivers subnanosecond pulses, whose duration is shortened in a standard optical fiber before amplification in a 3D multipass amplifier. This technique permits the generation of picosecond optical pulses with several tens of microjoules and kilohertz repetition rates. Rectangular electrical picosecond pulses with kilovolt positive and negative amplitudes are obtained with particular shapes and bipolar electrical pulses.