This PDF file contains the front matter associated with SPIE Proceedings Volume 8552, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Spectral and power characteristics of QD stripe lasers operating in two-state lasing regime have been studied in a wide range of operation conditions. It was demonstrated that neither self-heating nor increase of the homogeneous broadening are responsible for quenching of the ground-state lasing beyond the two-state lasing threshold. It was found that difference in electron and hole capture rates strongly affects light-current curve. Modulation p-type doping is shown to enhance the peak power of GS lasing transition. Microring and microdisk structures (D = 4-9 μm) comprising 1.3 μm InAs/InGaAs quantum dots have been fabricated and studied by μ-PL and NSOM. Ground-state lasing was achieved well above root temperature (up to 380 K). Effect of inner diameter on threshold characteristics was evaluated.

We present the investigation results on the nonlinear phase and chirp dynamics in semiconductor optical amplifiers (SOAs). Time-resolved gain and phase dynamics of a quantum well SOA are measured using 2 ps pump pulses into an integrated Mach-Zehnder interferometer switch under a co-propagation arrangement. Ultrafast component in the phase recovery is clearly observed. We explain the ultrafast phase dynamic by using a field propagation numerical model that includes the impact of sub-picosecond intra-band effects of the SOA. In addition, we investigate the chirp properties of the SOA in all-optical switches, and analyze the influences of chirp dynamics upon the detuned-filtering-based optical switches that extract the ultrafast chirp component to realize more than 160 Gbit/s optical switching. The results are very useful for SOA-based ultrafast optical signal processing in photonic networks.

The bandwidth-induced communication bottleneck due to the intrinsic limitations of metal interconnects is inhibiting the performance and environmental friendliness of today´s supercomputers, data centers, and in fact all other modern electrically interconnected and interoperable networks such as data farms and "cloud" fabrics. The same is true for systems of optical interconnects (OIs), where even when the metal interconnects are replaced with OIs the systems remain limited by bandwidth, physical size, and most critically the power consumption and lifecycle operating costs. Vertical-cavity surface-emitting lasers (VCSELs) are ideally suited to solve this dilemma. Global communication providers like Google Inc., Intel Inc., HP Inc., and IBM Inc. are now producing optical interconnects based on VCSELs. The optimal bandwidth per link may be analyzed by by using Amdahl´s Law and depends on the architecture of the data center and the performance of the servers within the data center. According to Google Inc., a bandwidth of 40 Gb/s has to be accommodated in the future. IBM Inc. demands 80 Tbps interconnects between solitary server chips in 2020. We recently realized ultrahigh bit rate VCSELs up to 49 Gb/s suited for such optical interconnects emitting at 980 nm. These devices show error-free transmission at temperatures up to 155°C and operate beyond 200°C. Single channel data-rates of 40 Gb/s were achieved up to 75°C. Record high energy efficiencies close to 50 fJ/bit were demonstrated for VCSELs emitting at 850 nm. Our devices are fabricated using a full three-inch wafer process, and the apertures were formed by in-situ controlled selective wet oxidation using stainless steel-based vacuum equipment of our own design. assembly, and operation. All device data are measured, recorded, and evaluated by our proprietary fully automated wafer mapping probe station. The bandwidth density of our present devices is expected to be scalable from about 100 Gbps/mm² to a physical limit of roughly 15 Tbps/mm² based on the current 12.5 Gb/s VCSEL technology. Still more energy-efficient and smaller volume laser diode devices dissipating less heat are mandatory for further up scaling of the bandwidth. Novel metal-clad VCSELs enable a reduction of the device's footprint for potentially ultrashort range interconnects by 1 to 2 orders of magnitude compared to conventional VCSELs thus enabling a similar increase of device density and bandwidth.

As an active research field, the self-mixing interferometry (SMI) based on semiconductor lasers (SLs) is a highly promising and emerging technique for non-contact sensing and parameter measurement of SLs. The basic structure of an SMI system consists of an SL, a lens and an external target. When a portion of reflected light from the target travels back to the laser cavity, a new lasing field is built up leading to both amplitude and phase modulations. The modulated output power is called a self-mixing signal which carries the information of both the target and SL’s feature parameters. Alpha factor, also known as linewidth enhancement factor, is one of the most important SL’s feature parameters. It characterizes the characteristics of SLs, such as the linewidth, the chirp, the injection lock range and the dynamic performances. This paper presents a new method for retrieving alpha factor of SLs by making use of a self-mixing interference (SMI) waveform. According to the well-known Lang-Kobayashi (L-K) theory, the SMI waveform is shaped by multiple parameters, including the alpha, the optical feedback level factor (denoted as C) and other parameters related to the oscillation of the external target. In this work, we build a new equation based on the SMI model derived from the L-K theory, which can be used to calculate the alpha value. In the existing SMI based methods for measuring the alpha factor, the optical feedback level C is limited within a certain narrow range. The proposed method is able to relieve this limitation. The associated simulations and experiments are carried out for verifying the proposed method.

Performance improving for monolithic two-section passively mode-locked (ML) quantum dot lasers has been systematically investigated using the Finite-Difference Traveling-Wave numerical model. Two approaches have been considered. For the first case, we changed simultaneously the length of the saturable absorber and the output facet reflectivity. We demonstrate that, by properly choosing these two parameters, a reduction of the pulse width from 3.4 ps to 1.1 ps and an increase the peak power 1 W to 1.6 W were obtained. For another case, we exchanged the optical power reflectivities at two end facets. We found that this approach can be used to further improve the ML stability for devices considered in the first approach where trailing edge instability is the main restriction.

Based on the band gap theory, a dual-wavelength VCSELs with same direction, equal-intensity, high-Q program is presented. The wavelengths of the VCSEL can be located with the aid of the Al_0.8Ga_0.2As defect layer in 1D photonic crystal structure. The results indicated that one-dimensional PC with a sheet of defect layer provides a parent structure on which laser beam can be well engineered without the expense of the macroscopic structural integrity.

A scheme for improving the self-induced polarization rotation (SPR) in a semiconductor optical amplifier (SOA) based on holding beam injection is proposed. Gain recovery of TE and TM modes can be largely accelerated through an appropriate holding beam injection, with which the response of SPR in the SOA for ultrafast signal can be speeded up. Holding beam injection is employed in SPR-based optical power equalization as an example of validation, in which the distortion of RZ (return-to-zero)and the overshoot of NRZ (non-return-to-zero) signal are largely suppressed, and the extension ratio are improved by 10 dB and 7 dB, respectively.

In this paper, a single facet slotted Fabry-Perot (FP) laser is demonstrated to provide tunable, single mode operation and has been monolithically integrated into a photonic integrated circuit (PIC) with semiconductor optical amplifiers and a multimode interference coupler. These lasers are designed by incorporating slots into the ridge of traditional FP cavity lasers to achieve single mode output, integrability and tunability. With the feature size of the slots around 1μm, standard photolithographic techniques can be used in the fabrication of the devices. This provides a time and cost advantage in comparison to ebeam or holographic lithography as used for defining gratings in distributed feedback (DFB) or distrusted Bragg reflector (DBR) lasers, which are typically used in PICs. The competitive integrable single mode laser also enables the PIC to be fabricated using only one epitaxial growth and one etch process as is done with standard FP lasers. This process simplicity can reduce the cost and increase the yield.

In order to obtain high power semiconductor lasers with narrow far-field and improve the characteristics of the output beam, a broad-stripe distributed feedback semiconductor laser with second-order metal surface gratings emitting around 940 nm is fabricated, based on the holographic photolithography and wet etching technology. The second-order metal gratings are located at the metal/semiconductor interface in the p-Al0.2GaIn0.49P cladding layer, with 960 μm×142 μm grating area, and the metal gratings also act as ohmic contact of the p side. The grating period is 287nm, the grating depth is 120 nm, and the grating duty cycle is 0.5. For the laser with second-order metal gratings, the powers is 718 mW, spectral linewidth (FWHM) is less than 0.1 nm, lateral far field angle (FWHM) is 2.7° and the vertical far-field angle (FWHM) is 16.7° in the current of 1.5 A. For the laser without gratings in the current of 1.5 A, the spectral linewidth is 1.3 nm, the lateral far-field angle is 7.3° and the vertical far-field angle is 36°, both worse than lasers with second-order metal surface gratings.

The monolithic integrated of four channel 1.55- μm range InGaAsP/InP distributed feedback lasers with a 4 × 1 multimode interference (MMI) optical combiner and semiconductor optical amplifier (SOA) using varied width ridge method, butt-joint technique and holographic exposure is proposed and demonstrated. The average output power and the threshold current are 1.8mW and 35mA, respectively, when the injection current of SOA is 100mA, with over 40-dB side mode suppression ratio (SMSR). The lasing wavelength is 1.55-μm range and 40dB sidemode suppression ratio (SMSR) is obtained. The four channels can operated separately or simultaneously.

Time-delay (TD) signatures of chaotic output in 1550nm vertical-cavity surface-emitting lasers (VCSELs) with double variable-polarization optical feedback (DVPOF) are investigated theoretically by using self-correlation function (SF). The effects of delay feedback time, feedback strength, polarizer angle, and injection current on the TD signature are discussed comprehensively. As a result, the optimal parameters setting for the TD signature suppression have been specified.

The dynamic control for the spectra of the Ultra-wideband (UWB) signals, which is the key for implementing the dynamic spectrum access in the cognitive radio, is still a challenge due to the limited processing speed of the electronic devices. In this paper, we have summarized our recent work about controlling the spectrum shape of the UWB signals in optical domain, in addition to reviewing the other groups’ related research work. The experiment setups and results based on nonlinear dynamics of the optoelectronic oscillator and transfer response of the phase or polarization-to-intensity convertor will be described in detail respectively, in which the controllable frequency suppress for the optical UWB signals at specific frequency positions were implemented. Particularly, the UWB pulse with the special shape, which corresponds to the 5-GHz band-rejection in frequency domain, was generated in order to avoid the interference between UWB and Wireless Fidelity system in practice. In addition, the UWB signals whose center frequency could be continuously tuned and converted up to the frequency range of millimeter wave were generated by utilizing the polarization modulator based optical switch. The areas for future development and the challenge of implementing these techniques for the applications in practice will also be discussed.

In this paper, a high-speed data acquisition system based on the technology of USB2.0 (Universal Serial Bus) is designed, in which USB master logic is implemented in an FPGA (Field Programmable Gate Array). Firstly, the hardware of data acquisition system is discussed, which includes chip selection, data acquisition and transmission circuit and power conversion circuit. Secondly, the corresponding software including USB firmware program, USB device driver and application program as well as its modifications have been described. The designed hardware and software will help to achieve a data acquisition system with the characterstics of high speed and high accuracy, etc.

Semiconductor lasers in chaotic oscillations have recently been utilized for random bit generation at output rates exceeding gigabits per second, which are important for high-speed numerical simulation, encryption, and communication. Although chaotic signals were successfully invoked though optical feedback into the lasers, the feedbacks inherently led to residual autocorrelation that is detrimental to the output randomness. In this paper, we experimentally demonstrate random bit generation using an optically injected semiconductor laser without feedback. Through oversampling the signal at 10 GHz as recorded by a 2.5-GHz oscilloscope, random bit generation at 40 Gbps is attained from extracting 4 bits per sample.

A Raman remote spectroscopy system was realized using flexible hollow optical fiber as laser emittion and signal collection probes. A silver-coated hollow fiber has low-loss property and flat transmission characteristics in the visible wavelength regions. Compared with conventional silica optical fiber, little background fluorescence noise was observed with optical fiber as the probe, which would be of great advantages to the detection in low frequency Raman shift region. The complex filtering and focusing system was thus unnecessary. The Raman spectra of CaCO₃ and PE were obtained by using the system and a reasonable signal to noise ratio was attained without any lens. Experiments with probes made of conventional silica optical fibers were also conducted for comparisons. Furthermore, a silver-coated hollow glass waveguide was used as sample cell to detect liquid phase sample. We used a 6 cm-long hollow fiber as the liquid cell and Butt-couplings with emitting and collecting fibers. Experiment results show that the system obtained high signal to noise ratio because of the longer optical length between sample and laser light. We also give the elementary theoretical analysis for the hollow fiber sample cell. The parameters of the fiber which would affect the system were discussed. Hollow fiber has shown to be a potential fiber probe or sample cell for Raman spectroscopy.

All-optical sampling attracts considerable attention due to its crucial applications in high-speed optical analog-to-digital conversion. We present an all-optical sampling scheme using a single semiconductor optical amplifier. In the experiment, 40 GSa/s all-optical sampling for 2.5 GHz analog optical signal is successfully demonstrated with commercially available fiber-pigtailed components. The all-optical sampling shows a fundamental conversion efficiency of 1.35 and a total harmonic distortion of 2.01% at the operating power of 5 mW. Our scheme requires only one semiconductor optical amplifier and has low power consumption, which shows much potential for the high-speed optical analog-to-digital conversion.

A bidirectional chaos communication system, composed of 1550nm semiconductor lasers (SLs) and fiber links, is experimentally and numerically investigated. Based on the robust chaos synchronization between two authorized SLs, 0.5Gbits/s pseudo-random data bidirectional message transmission between the two SLs has been preliminarily realized experimentally. Moreover, related theoretical simulations are also given, which basically conforms to our experimental observations.

A laser array, which is consisted of 56 π equivalent phase shift (EPS) sampled Bragg grating (SBG) semiconductor laser, is experimentally investigated. The experimental results show the influence of the sampling duty cycle fabrication error on the lasing wavelength of an SBG semiconductor laser can be ignored.

It has been demonstrated experimentally that pulsed pumping can significantly improve the thermal management in an optically-pumped semiconductor disk laser, and the output power of semiconductor disk lasers under pulsed pumping can be upgraded to times of those under continuous pumping. This paper presents numerical analysis of the thermal effects of pulsed pumping in semiconductor disk lasers, so to theoretically disclose the details of the thermal processes of pulsed pumping. In the simulation, the parabolic heat conduction equation, which is widely employed to describe the transient thermal transfer processes, is solved under cylindrical coordinates by the use of the finite element method, a periodic pump pulses train is assumed, and the maximum temperature rise in the multiple quantum wells active region is focused. The influences of the duty cycle, the repetition rate, and the pulse width of the pump pulses on the maximum temperature rise are investigated, and the results are compared with the case of continuous-wave pumping. Some simulation results are compared with reported data, and the theoretical results are in good agreement with the experiments.

Low threshold, continuous wavelength tuning micro-electro-mechanically system (MEMS) tunable vertical-cavity surface-emitting lasers (VCSELs) operating at 980 nm are demonstrated. The device utilizes the two-chip concept with a MEMS membrane mirror suspended by an air gap above a VCSEL amplifier. Output power of 4.56 mW with 14μm diameter oxide aperture in continuous operation and tuning range of 6.8nm are obtained. Due to the low optical loss in resonance cavity results in threshold current as low as 0.6 mA at room temperature. Theoretical calculation for the threshold gain as a function of the wavelength and air gap is obtained respectively, which provides the design strategies to improve device performance.

For developing the tunable performance and stability, we present a widely tunable 850nm-range VCSEL structure based on the voltage-dependent birefringence of liquid crystal. An intracavity liquid crystal layer is imbedded between the top DBR (Distributed Bragg Reflector) and the Half VCSEL as an electro-optic index modulator. An Al0.98Ga0.02As oxidization layer was grown above the active region for current and optical confinement. By the calculation, we found tuning efficiency increased after thickening the liquid crystal layer. However, the optical loss in resonance cavity also increased simultaneously. For compromise, we got that 1837nm is the most suitable thickness. And the tuning efficiency is obviously larger than the electrostatic method. Then, we calculated the electric field intensity distribution, the gain characteristics of GaAs/Al0.3Ga0.7 As quantum wells and the threshold features when thickness of liquid crystal layer is 1837nm. By analyzing these results, tuning efficiency of 5.4nm/V and 15nm tuning range are obtained at last. Our study could provide insight into tunable VCSELs design and optimization.

A novel mode-beating DBR laser with dual-mode lasing is fabricated. The DBR laser has four parts, a front gain section, a phase section, a DBR grating section, and a rear gain section. When the current of the front gain section is above the threshold, the device is working in single-mode. Dual-mode lasing can be obtained by adjusting the current of the rear gain section. The power difference between the two modes can be less than 1 dB. An optical down-conversion technique was used to measure the beating frequency. The mode-beating frequency of the two modes is about 93 GHz, and the 3- dB linewidth of the mode-beating RF spectrum of the laser when free-running is about 5 MHz. Moreover, the wavelength of the dual-mode can be tuned synchronously when the current injected into the DBR grating section is adjusted. The wavelength tuning range of the device is at least 3 nm.

To understand the physical process of SRS lasing in SOI waveguides and to optimize the performance of continuouswave Raman silicon lasers, in this paper numerical simulation on the output characteristics of continuous-wave Raman silicon lasers with different parameters is performed. Based on power propagation equations in SOI waveguides and boundary conditions, the output powers as functions of the launched pump power, the gain length, the reflectivity of the output end, and the effective mode area of the SOI waveguide are presented. It is shown that two-photon absorption (TPA) and free-carrier absorption (FCA) lead to a significant reduction to the output power of continuous-wave Raman silicon lasers, which is in good agreement with the experimental reports. Numerical analysis predicts that in the absence of TPA and FCA there are optimum values for the silicon waveguide length, the effective mode area and the output reflectivity, respectively.

The amplified Spontaneous Emission (ASE) is the important noise source for EDFA, affecting the EDFA based fiber laser seriously. The theory and practice have shown that the ASE is closely related with pump methods, so the study on the ASE of EDF under the condition of the pulse pumping has important academic significations. What’s more, the mode-locked laser based on EDFA fiber ring could be pumping by the pulse to realized mode-lock, and the ASE will impact its characteristics. In this paper, the effects of pump pulse with different width and amplitude on the ASE were investigated by the theoretical and experiment methods. Beginning with the carrier density rate equation, we can get each level of the distribution of the number of particles carriers along with the change of time based on the relationship between the average number of photons of the spontaneous radiation and the number of particles carriers distribution. An approximate analytic solution of output ASE noise average is derived when pump signal is small.Building an experimental system, the results show that the output amplitude of ASE is proportional to the input width of pump pulse when the pump pulse is small. It's also shows that the output amplitude of ASE is proportional to the input amplitude of pump pulse. The new phenomena can be used for the all-optical measurement of a pulse width.

In the paper, a design scheme of driving circuit and collimating optical system used for 3D (three-dimensional) imaging device has been proposed. The driving circuit based on power MOSFET for high-power pulsed laser diode has the characteristics of short pulse-width and high output current. According to semiconductor laser’s far field divergence characteristic, the aspheric collimation part has been designed by using optical design software ZEMAX. Far field beam tracing and collimation results are simulated. The laser driver’s output current and pulse width are about 144A and 13.9ns respectively. The RMS of divergent angle of simulation in ZEMAX is 0.318mrad and the spot is more uniform.

A semiclassical approach is used to calculate the principle for heterodyne detection utilizing two optical detectors. These calculations show that excess-noise in the local-oscillator can be canceled and the balanced-detector optical heterodyne detection requires less local oscillator power compared with the traditional single-detector optical heterodyne detection. An experimental demonstration of excess-noise cancellation is reported.

In this paper, far field speckle contrast from a broad area laser diode is measured. The intensity of the incident laser light onto a diffuser is controlled by using polarizer or adjusting input current. A rectangular aperture close to diffuser is used to select different parts of laser light field as illumination spot. The speckle contrast measured for different illuminationspots has no significant change. When the laser diode operates at its typical power output condition, the speckle contrast measured approximately equals 1, while the speckle contrast is depressed tremendously when the laser diode operates with low driving current.