Adaptive split-step Fourier method for simulating ultrashort laser pulse propagation in photonic crystal fibres

In this paper, the generalized nonlinear Schrodinger equation （GNLSE） is solved by an adaptive split-step Fourier method （ASSFM）. It is found that ASSFM must be used to solve GNLSE to ensure precision when the soliton selffrequency shift is remarkable and the photonic crystal fibre （PCF） parameters vary with the frequency considerably. The precision of numerical simulation by using ASSFM is higher than that by using split-step Fourier method in the process of laser pulse propagation in PCFs due to the fact that the variation of fibre parameters with the peak frequency in the pulse spectrum can be taken into account fully.

The single-longitudinal-mode operation of a ridge waveguide laser based on two-dimensional photonic crystals

An electrically driven, single-longitudinal-mode GaAs based photonic crystal （PC） ridge waveguide （RWG） laser emitting at around 850 nm is demonstrated. The single-longitudinal-mode lasing characteristic is achieved by introducing the PC to the RWG laser. The triangle PC is etched on both sides of the ridge by photolithography and inductive coupled plasma （ICP） etching. The lasing spectra of the RWG lasers with and without the PC are studied, and the result shows that the PC purifies the longitudinal mode. The power per facet versus current and current-voltage characteristics have also been studied and compared.

Photonic crystal fibre Brillouin laser based on Bragg grating Fabry-Perot cavity

A photonic crystal fibre Brillouin laser based on fibre Bragg grating Fabr-Perot cavity is presented. A highly nonlinear photonic crystal fibre 25 m in length is used as Brillouin gain medium and fibre Bragg grating Fabry-Perot cavity is chosen in order to enhance the laser conversion efficiency and suppress the higher-order Stokes waves. The laser reaches the threshold at input power of 35 mW, and the experimental laser conversion efficiency achieves 18% of the input power of 140 mW and does not show higher-order Stokes waves. A photonic crystal fibre Brillouin laser with shorter fibre length and lower threshold is experimentally realized.

Generation of wideband tunable femtosecond laser based on nonlinear propagation of power-scaled mode-locked femtosecond laser pulses in photonic crystal fiber

We implement an experimental study for the generation of wideband tunable femtosecond laser with a home-made power-scaled mode-locked fiber oscillator as the pump source.By coupling the sub-100 fs mode-locked pulses into a nonlinear photonic crystal fiber(NL-PCF),the exited spectra have significant nonlinear broadening and cover a spectra range of hundreds of nm.In experiment,by reasonably optimizing the structure parameters of NL-PCF and regulating the power of the incident pulses,femtosecond laser with tuning range of 900-1290 nm is realized.The research approach promotes the development of femtosecond lasers with center wavelengths out of the traditional laser gain media toward the direction of simplicity and ease of implementation.

Semiconductor photonic crystal laser

By combing artificial micro–nano structures, photonic crystals（PCs）, with traditional semiconductor laser material to realize the dynamic collaborative control of photonic states and confined electrons, the band engineering of the PC has been confirmed. This brings new development space for the semiconductor laser, such as for low threshold and high efficiency.Based on a series of works by Zheng＇s group, this paper has reviewed kinds of PC lasers including electrical injection PC vertical cavity and lateral cavity surface-emitting lasers, and PC high beam quality lasers, to show that the PC is vital for promoting the continuous improvement of semiconductor laser performance at present and in the future.

Vertical cavity surface emitting laser transverse mode and polarization control by elliptical hole photonic crystal

The polarization of traditional photonic crystal（PC） vertical cavity surface emitting laser（VCSEL） is uncontrollable,resulting in the bit error increasing easily.Elliptical hole photonic crystal can control the transverse mode and polarization of VCSEL efficiently.We analyze the far field divergence angle,and birefringence of elliptical hole PC VCSEL.When the ratio of minor axis to major axis b/a = 0.7,the PC VCSEL can obtain single mode and polarization.According to the simulation results,we fabricate the device successfully.The output power is 1.7 mW,the far field divergence angle is less than 10°,and the side mode suppression ratio is over 30 dB.The output power in the Y direction is 20 times that in the X direction.

Efficient frequency upshift of 10 fs laser pulses propagating in a 5-cm length birefringent photonic crystal fibre

This paper reports that a 5-cm length birefringent photonic crystal fibre is used to tune the output frequency of unamplified 10-fs Ti：sapphire pulses. The zero dispersion of the fibre is at 823 nm and 800 nm for slow and fast fundamental modes, respectively. It is demonstrated that efficient upshift of the output frequency can be achieved when the pumped radiation is polarized along the slow axis of the fibre. When the average input power reaches 320 mW, about 60% of the output energy is located in one peak at 600 nm and is accompanied by depletion of the pulse inside the anomalous dispersion region.

Fiber optical parametric oscillator based on photonic crystal fiber pumped with all-normal-dispersion mode-locked Yb:fiber laser

We demonstrate a cost effective, linearly tunable fiber optical parametric oscillator based on a home-made photonic crystal fiber pumped with a mode-locked ytterbium-doped fiber laser, providing linely tuning ranges from 1018 nm to 1038 nm for the idler wavelength and from 1097 nm to 1117 nm for the signal wavelength by tuning the pump wavelength and the cavity length. In order to obtain the desired fiber with a zero dispersion wavelength around 1060 rim, eight sam- ples of photonic crystal fibers with gradually changed structural parameters are fabricated for the reason that it is difficult to accurately customize the structural dimensions during fabrication. We verify the usability of the fabricated fiber experimen- tally via optical parametric generation and conclude a successful procedure of design, fabirication, and verification. A seed source of home-made all-normal-dispersion mode-locked ytterbium-doped fiber laser with 38.57 ps pulsewidth around the 1064 nm wavelength is used to pump the fiber optical parametric oscillator. The wide picosecond pulse pump laser enables a larger walk-off tolerance between the pump light and the oscillating light as well as a longer photonic crystal fiber of 20 m superior to the femtosecond pulse lasers, resulting in a larger parametric amplification and a lower threshold pump power of 15.8 dBm of the fiber optical parametric oscillator.

Photonic crystal fiber Mach-Zehnder interferometer with microholes ablated by a femtosecond laser for refractive index sensing

A new structure of the photonic crystal fiber（PCF）based Mach-Zednder interferometer（MZI）is fabricated and presented.The structure has microholes ablated by a femtosecond laser.The fringe visibility can be enhanced more than 10 dB compared with the interferometer without a microhole.The interferometer is characterized by sodium chloride solutions for refractive index（RI）sensing.The RI sensitivities are greatly increased by the hole fabrication since it directly changes the cladding modes of the PCF.For the interferometer sensor with two holes,the RI sensitivity is 157.74 nm/RIU,which is 5 times than that of the sensor without a microhole.Microholes ablation with a femtosecond laser on PCF can increase the sensor＇s sensitivity dramatically.Femtosecond laser has a wide application prospect in the field of performance improvement of the sensors.

Simplified modeling of frequency behavior in photonic crystal vertical cavity surface emitting laser with tunnel injection quantum dot in active region

In this work, the characteristics of the photonic crystal tunneling injection quantum dot vertical cavity surface emitting lasers（Ph C-TIQD-VCSEL） are studied through analyzing a modified modulation transfer function. The function is based on the rate equations describing the carrier dynamics at different energy levels of dot and injector well. Although the frequency modulation response component associated with carrier dynamics in wetting layer（WL） and at excited state（ES） levels of dots limits the total bandwidth in conventional QD-VCSEL, our study shows that it can be compensated for by electron tunneling from the injector well into the dot in TIQD structure. Carrier back tunneling time is one of the most important parameters, and by increment of that, the bias current dependence of the total bandwidth will be insignificant. It is proved that at high bias current, the limitation of the WL-ES level plays an important role in reducing the total bandwidth and results in rollovers on 3-d B bandwidth-I curves. In such a way, for smaller air hole diameter of photonic crystal, the effect of this reduction is stronger.

Static and Dynamic Analysis of Lasing Action from Single and Coupled Photonic Crystal Nanocavity Lasers

The single and coupled photonic crystal nanocavity lasers are fabricated in the InGaAsP material system and their static and dynamic features are compared. The coupled-cavity lasers show a larger lasing e^ciency and generate an output power higher than the single-cavity lasers, results that are consistent with the theoretical results obtained by rate equations. In dynamic regime, the single-cavity lasers produce pulses as short as 113 ps, while the coupled-cavity lasers show a significantly longer lasing duration. These results indicate that the photonic crystal laser is a promising candidate for the light source in high-speed photonic integrated circuit.

Stable CW Single-Mode Photonic Crystal Fiber DFB Ring Laser

We demonstrate stable single-mode CW operation of a DFB ring laser based on Er3＋ doped photonics crystal fiber （PCF）. The incorporation of a ring cavity allows one single mode to lase and also suppresses the unwanted effect of self-pulsing. Such a narrow linewidth source in PCF has great potential in spectroscopy.

Application of Photonic Crystals in Semiconductor Lasers

Photonic crystals(PCs) have attracted much considerable research attention in the past two decades. They are artificially fabricated periodic dielectric structures. The periodic dielectric structures have photonic band gap(PBG) and are referred to as photonic band gap materials. This paper mainly introduces one-dimensional (1-D) and 2D PCs applied in the semiconductor lasers.

Recent developments in high power near-infrared super-continuum generation based on photonic crystal fiber

High power supercontinuum generation has witnessed rapid developments during the past few years. The mecha- nism and the latest achievements in high power supercontinuum generation are reviewed both for the continuous wave pump regime and the pulsed pump regime. The challenges in scaling the average power of supereontinuum generation are analyzed. Some of our works on high power supercontinuum generation are summarized, and perspectives for the future development are discussed.

Generation of a compact high-power high-efficiency normal-dispersion pumping supercontinuum in silica photonic crystal fiber pumped with a 1064-nm picosecond pulse

Broadband normal dispersion pumping supercontinuum （SC） generation in silica photonic crystal fiber （PCF） is investigated in this paper. A 1064-nm picosecond fiber laser is used to pump silica PCF for the SC generation. The length of PCF is optimized for the most efficient stimulated Raman scattering process in the picosecond pump pulse region. The first stimulated Raman Stokes peak is located in the anomalous dispersion regime of the PCF and near the zero dispersion wavelength; thus the SC generation process can benefit from both a normal dispersion pumping scheme and an anomalous dispersion pumping scheme. The 51.7-W SC spanning from about 700 nm to beyond 1700 nm is generated with an all-fiber configuration, and the pump-to-SC conversion efficiency is up to 90%. In order to avoid the output fiber end face damage and increase the stability of the system, an improved output solution for the high power SC is proposed in our experiment. This high-efficiency near-infrared SC source is very suitable for applications in which average output power and spectral power density are firstly desirable.

Reseach Progress of Photonic Crystal Fibers in China

Photonic Crystal Fibers have attracted worldwideinterest within the last decade due to their uniqueoptical properties and because they exhibit a muchhigher degree of design freedom compared to conventionaloptical fibers.In this article, the fabricationtechnologies of photonic crystal fibers and theirapplications at home and abroad were formulated atlength, especially in the following fields, such aslarge mode area active photonic crystal fibers andfiber lasers, birefringence fibers and sensors, highnonlinear photonic crystal fibers and frequencytransformation, dispersion compensation PCFs anddispersion compensation for telecommunicationsystems, and photonic band-gap fibers. Finally, accordingto the above analysis, the prospects anddeveloping trends of photonic crystal fibers in thefuture were presented.

Optical parametric chirped pulse amplification based on photonic crystal fibre

A compact two-stage optical parametric chirped pulse amplifier based on photonic crystal fibre is demonstrated. A 1064-nm soliton pulse is obtained in a home-made photonic crystal fibre （PCF） with femtosecond pulse pumping and then amplified to 2 mJ in an Nd：YAG regenerative amplifier. After the amplified pulses pass through the LBO crystal, the 532-nm double-frequency light with an energy of 0.8 mJ and a duration of over 100 ps at 10-Hz repetition rate is generated as a pump source in the following two-stage optical parametric amplification （OPA）. The 850-nm chirped signal light gain from the stretcher is 1.5 × 10^4 in the first-stage OPA while it is 120 in the second-stage OPA. The total signal gain of optical parametric chirped pulse amplification （OPCPA） can reach 1.8 × 10^6.

Femtosecond laser direct writing of flexibly configured waveguide geometries in optical crystals:fabrication and application

Optical waveguides are far more than mere connecting elements in integrated optical systems and circuits.Benefiting from their high optical confinement and miniaturized footprints,waveguide structures established based on crystalline materials,particularly,are opening exciting possibilities and opportunities in photonic chips by facilitating their on-chip integration with different functionalities and highly compact photonic circuits.Femtosecond-laser-direct writing(FsLDW),as a true three-dimensional(3D)micromachining and microfabrication technology,allows rapid prototyping of on-demand waveguide geometries inside transparent materials via localized material modification.The success of FsLDW lies not only in its unsurpassed aptitude for realizing 3D devices but also in its remarkable material-independence that enables cross-platform solutions.This review emphasizes FsLDW fabrication of waveguide structures with 3D layouts in dielectric crystals.Their functionalities as passive and active photonic devices are also demonstrated and discussed.

Photonic crystal vertical-cavity surface-emitting laserbased on GaAs material

A photonic crystal vertical-cavity-surface-emitting laser (PC-VCSEL) with a wavelength of about 850 nm was realized. The direct-current electrically-driven PC-VCSELs with a minimum threshold current of 2 mA and a maximum threshold current of 13.5 mA were obtained. We fabricated a series of PC-VCSEL chips whose lattice constants are in the range from 0.5 to 3 μm with different filling factors, and found that the laser characterization depends on the lattice constant, the filling factor, the size of cavity, etc.

High-power ultraviolet 278-nm laser from fourth-harmonic generation of an Nd：YAG amplifier in CsB3O5 crystal

We report on the experimental investigation and theoretical analysis of a nanosecond pulse high power ultraviolet（UV） 278 nm laser by fourth-harmonic generation（FHG） of a 1112-nm Nd：YAG amplifier in LiB3O5（LBO） and CsB3O5（CBO） crystals. The UV laser delivers a maximum average power of 10.3 W at 278 nm with peak power of 36.8 k W under input pump power of 41 W at 556 nm. This is, to the best of our knowledge, the highest output power at the specific UV wavelength of 278 nm. We also performed the theoretical investigation on the FHG with a model in the Gaussian approximation of both spatial and temporal profiles, especially accounting for the two-photon absorption effect in CBO crystal for the first time. The average output power, pulse width, and beam spatial distribution of the UV laser were simulated. The theoretical calculations are in close agreement with the experimental results.