Semiconductor Laser Sources Research Articles

Adiabatic weak coherent MHz linewidth O-band single-photon carrier for low erroneous phase decoding

For weak coherent single-photon secure data communication among short-reach metropolitan intra-/inter-city networks at the O-band (1250-1350 nm), the commercially available semiconductor laser sources are emerging but still suffering from high single-mode-fiber (SMF) loss, broad linewidth, and unstable wavelength. To overcome such disadvantages for enabling the efficient phase-coding link with sufficient secure key rate, a specifically designed adiabatic package with active temperature-/current-feedback control is proposed for the paired O-band MHz-linewidth master-to-slave injection-locked DFBLDs and a polarization-maintaining 1-bit-delay interferometer is stabilized with using a passively adiabatic cell to achieve accurate differential phase decoding. Even though, the phonon-induced phase fluctuation still occurs at rising and falling edges of the decoded long-pattern secure data bits delivered from the slave DFBLD, which is mainly attributed to the intra-cavity heating under excessive free-carrier generation via the master DFBLD injection. To stabilize the differential-phase-shift (DPS) keying protocol, the phase-code distortion caused by over-injection-induced Auger heating is effectively suppressed by reducing the overly biased injection with precise master-injection-level control. The rising-/falling-edge damping distortion of the phase-shift-encoded secure bit-stream envelope is suppressed by appropriately decreasing the DC bias current and adjusting the AC encoding amplitude of the master DFBLD. Such operation reduces the incorrect π phase shift in the injection-locked slave DFBLD biased at optimized below-threshold DC offset, thus allowing single-photon DPS-keying data transmission over 15-km SMF with slightly increasing the single-photon bit-error ratio from <3% (0-km) to 6.2% (15-km).

Quantum cascade disk and ring lasers

Quantum cascade lasers (QCLs) are a prominent semiconductor laser source operating in the mid-infrared and terahertz regimes. As is typical with semiconductor lasers, QCLs usually monolithically integrate the active gain material and the resonator. Hence, over nearly 30 years of QCL development, resonator geometries have developed alongside active region designs. Disk and ring geometries, in particular, have long been recognized for their unique attributes, which have, in turn, contributed to the demonstration of ultra-small cavities as well as surface emission from QCLs. In recent years, ring geometries have witnessed a resurgence as promising platforms for frequency comb and soliton generation as well as mid-infrared photonic integration. In this Perspective, we describe the attributes that make ring and disk QCLs unique by discussing key demonstrations. We present recent results, which indicate that these devices are poised to become building blocks of highly integrated, next-generation spectrometers operating in the mid-infrared. We discuss promising avenues for future research centered around monolithic ring and disk-type QCLs in applications ranging from gas sensing and spectroscopy to quantum optics and non-Hermitian photonics.

High‑Brightness Blue Semiconductor Laser Source Based on Grating Spectral Beam Combining

High‑Brightness Blue Semiconductor Laser Source Based on Grating Spectral Beam Combining

Wide‐Wavelength Tunable Mid‐Infrared Lasing Based on Black Arsenic Phosphorus

AbstractMid‐infrared (MIR) semiconductor laser sources are essential for applications in gas detection, infrared imaging, and high‐speed free space optical communications. At present, the dynamic wavelength tunability of MIR lasers based on lead salt, antimonide, and quantum cascade lasers is limited and their compact size as well as heterogeneous integration are still challenging. Two‐dimensional (2D) materials, used as optical gain materials, have the flexible tunability and compatible van der Waals integrations—providing many new possibilities for constructing MIR laser sources of large tunability and high integration. Here, wide‐wavelength tunable MIR vertical cavity surface emitting lasers (VCSELs) integrated on silicon substrates are realized based on 2D black arsenic phosphorus (b‐AsxP1−x). The emission wavelength of the optically pumped laser device is demonstrated to be tuned from 3.42 to 4.65 µm at room temperature, which could be controlled by adjusting the alloy composition and thickness of the gain media b‐AsxP1−x. The tunable MIR VCSEL device would pave the way for further exploration of 2D materials‐based IR lasers working as on‐chip light sources.

High Q Resonances in a Metallically Coated Wave-Chaotic Microcavity

Optical resonances of a metallically coated wave-chaotic microcavity are investigated. Mode resonances with a low-contrast quality factor and distinct field patterns are demonstrated. Unlike the resonances in the dielectric chaotic-wave cavity where the refractive escape leads a high optical loss, the resonances in metallically coated cavity hold high quality factors with a low loss induced by metal dissipation. As a potential application, the metallically coated chaotic-wave microcavity could be used for a semiconductor laser source with dense modes lasing and accordingly a low spatial coherent emission.

Broadly tunable lens-coupled nonlinear quantum cascade lasers in the sub-THz to THz frequency range

Room-temperature terahertz (THz) quantum cascade laser sources with intracavity difference-frequency nonlinear mixing are electrically pumped monolithic semiconductor laser sources operating in the 0.6–6 THz spectral range. We report widely tunable, low-frequency THz quantum cascade laser sources using a lens-coupled Cherenkov waveguide scheme. Based on a watt-class high-power, λ ∼ 13.7 μm quantum cascade laser, the monolithic THz source is strongly coupled with a high-resistivity silicon lens, which causes a major increase in the THz coupling efficiency and demonstrates significant performance improvements. A room-temperature 1.5 THz device produces a 0.2 mW peak output power with a high-quality beam pattern. Improved THz outcoupling efficiency using the lens-coupled scheme enabled the demonstration of a high-performance external-cavity semiconductor THz source that is tunable from 420 GHz to 2 THz. The external-cavity, lens-coupled device configuration can technically be assembled into a butterfly-style package for a thumb-sized, widely frequency tunable THz semiconductor source.

Deep learning based optical curvature sensor through specklegram detection of multimode fiber

An optical fiber curvature sensor based on the detection of specklegrams from the facet of multimode fiber (MMF) is realized by using a deep learning regression model. Since the specklegrams result from mode interference in the MMF, they can be used to characterize the status of the MMF. In the experiment, light from a semiconductor laser source was injected into a section of 10-cm-long step-indexed MMF with a core diameter of 50 μm. A large number of specklegrams at the facet of the MMF were automatically detected when different curvatures were introduced for the MMF by a controllable moving translation stage. The output specklegrams of the MMF under different curvatures were then fed into a convolutional neural network (CNN) for training, validation and testing. Experimental results demonstrate that after the CNN was well-trained by the specklegrams with specified curvatures, the CNN can effectively predict the curvature from any of the specklegrams obtained from the MMF with a curvature in the trained range. In the experiment, the CNN trained by specklegrams with 20 curvatures successfully predicted the curvatures corresponding to the specklegrams from the MMF under 57 curvatures in the range of 1.55–6.93 m−1. The prediction error for 94.7% of the specklegrams is within an error range of ±0.3m-1, confirming the feasibility of curvature sensing based on the analysis of specklegrams by CNN.

Low FSR Mode-Locked Laser Based on InP-Si3N4 Hybrid Integration

Generation of optical frequency combs (OFC) using semiconductor laser sources has been an active research topic for years, since they offer good performances for many applications without the bulky and expensive aspects of ion doped fiber or crystal based laser sources. In this paper, we demonstrate the generation of low free spectral range mode-locked laser using hybrid III-V/Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> butt coupling. We start by describing the design and the fabrication process of the active R-SOA chip made at our laboratory, and the passive Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> chip having low losses measured to be around 6 dB/m. We then report the integration process and the results of passive mode locking. Our mode-locked laser has a repetition rate of 360 MHz, which is, to the best of our knowledge, the lowest repetition rate achieved for a hybrid integrated mode-locked laser. The frequency comb generated has a 30 dB bandwidth of 2.8 nm (349 GHz). Finally, we show the demonstration of active and harmonic mode locking up to the sixth harmonic.

Compressed-sensing fiber-optic white light interferometry.

In this Letter, we propose a dynamic fiber-optic white light interferometry (WLI) based on the compressed-sensing (CS) principle. The time-varying interference spectra of a Fabry-Perot cavity under vibration are considered as a two-dimensional (2D) signal with respect to both laser wavelength and time, which can be compressively sampled using a programmable semiconductor laser source during the measurement process. After CS reconstruction, the spectrum acquisition rate is equal to the random wavelength modulation rate, up to 10 MHz in this Letter, providing an attractive alternative to laser-based dynamic interferometry. Numerical simulations and nanometer-scale vibration experiments verify the effectiveness of the scheme.

Difference-frequency generation in an AlGaAs Bragg-reflection waveguide using an on-chip electrically-pumped quantum dot laser

Nonlinear frequency conversion is ubiquitous in laser engineering and quantum information technology. A long-standing goal in photonics is to integrate on-chip semiconductor laser sources with nonlinear optical components. Engineering waveguide lasers with spectra that phase-match to nonlinear processes on the same device is a formidable challenge. Here, we demonstrate difference-frequency generation in an AlGaAs Bragg reflection waveguide which incorporates the gain medium for the pump laser in its core. We include quantum dot layers in the waveguide that generate electrically driven laser light at ∼790 nm, and engineer the structure to facilitate nonlinear processes at this wavelength. We perform difference-frequency generation between 1540 nm and 1630 nm using the on-chip laser, which is enabled by the broad modal phase-matching of the AlGaAs waveguide, and measure normalized conversion efficiencies up to ()% W−1 cm−2. Our work demonstrates a pathway towards devices that utilize on-chip active elements and strong optical nonlinearities to enable highly integrated photonic systems-on-chip.

Gigahertz measurement-device-independent quantum key distribution using directly modulated lasers

Measurement-device-independent quantum key distribution (MDI-QKD) is a technique for quantum-secured communication that eliminates all detector side-channels, although is currently limited by implementation complexity and low secure key rates. Here, we introduce a simple and compact MDI-QKD system design at gigahertz clock rates with enhanced resilience to laser fluctuations—thus enabling free-running semiconductor laser sources to be employed without spectral or phase feedback. This is achieved using direct laser modulation, carefully exploiting gain-switching and injection-locking laser dynamics to encode phase-modulated time-bin bits. Our design enables secure key rates that improve upon the state of the art by an order of magnitude, up to 8 bps at 54 dB channel loss and 2 kbps in the finite-size regime for 30 dB channel loss. This greatly simplified MDI-QKD system design and proof-of-principle demonstration shows that MDI-QKD is a practical, high-performance solution for future quantum communication networks.

Pulse control of frequency and width for a real-time independently adjustable laser source

A set of semiconductor laser pulse seed sources based on an embedded chip is proposed. The greatest feature is that the optical pulse frequency and width can be independently adjusted in real time. The pulse seed sources can be switched independently and online from the gain-switched mode to the quasi-continuous wave mode to obtain optimal optical parameters for specific applications. To explore the physical mechanism of the semiconductor laser source, the rate equation that describes the carrier-photon transient change in a semiconductor laser cavity is numerically derived and solved. Subsequently, problems that need to be considered while designing the drive circuit are identified. The system evaluation indicates that the optical pulse frequency adjustment range is 250 Hz to 42 MHz, and the narrowest optical pulse output width is 80 ps. The pulse seed source can drive semiconductor lasers with different central wavelengths (1064, 1550, and 1970 nm), and can also simultaneously drive two semiconductor lasers and output dual-band optical pulses. It can be used as a seed source for general high-power optical systems, and exhibits good application value and extensive market prospects.

Recent Advances of Efficient Design of Terahertz Quantum-Cascade Lasers

Terahertz (THz) quantum cascade lasers (QCLs) are electrically pumped and heterostructure based semiconductor laser sources with intersubband transitions of electrons in different layers of the quantum wells and barriers. The THz QCLs have high output power in THz region which make them important from application point of view. Recently intensive research has been carried out by researchers for obtaining efficient designs of THz sources. Most of the researchers have investigated the THz frequency range between 0.1 and 3 THz; however, the output power of the THz sources in the frequency range 3–5 THz is small because of transit time and resistance-capacitance effects. Nevertheless, the present review is focused for the development of efficient THz QCL sources in the frequency range from 3 to 5 THz where one of the major problem of thermal backfilling of the carriers has to be overcome by engineering the heterostructure.

Crystal engineering and physicochemical properties of l-threoninium succinate (LTS) single crystal for frequency conversion applications

The synthesis and characterization of organic nonlinear optical active (NLO) single crystal of l-threoninium succinate (LTS) were carried out in this work. LTS crystal was prepared by slow evaporation technique using deionized water as solvent in a period of 82 days and the obtained LTS crystal was subjected to such characterizations as single-crystal X-ray diffraction analysis, UV–Vis–NIR spectroscopy analysis, FT-IR spectrum analysis, thermal analysis, second harmonic generation, and surface quality analysis. The third-order nonlinear optical properties of the LTS crystal were estimated at 532 nm using semiconductor laser source. Then it was employed for Z-scan analyzer to sense the nonlinear refractive index (n2), absorption coefficient (β), and third-order susceptibility (χ3). Through this analysis, this research calculated the n2 = 2.35 × 10–15 (m3/W), β = 1.3057 × 10–8 (m/W), and χ3 = 1.0571 × 10−13 (esu) were determined. The obtained results exhibited an appropriate variation in optical limiting behavior of the LTS material which saturates at higher intensities with respect to input and output power. The laser damaged threshold (LDT) technique enables the great resistivity toward optical high energy and it is found to be 52.7 mJ.

Mid-infrared laser diodes epitaxially grown on on-axis (001) silicon

The direct epitaxial growth of III-V semiconductor lasers on standard, CMOS-compatible, on-axis (001) Si substrates is actively sought for the realization of active photonic integrated circuits. Here we report on the first mid-infrared semiconductor laser epitaxially grown on on-axis Si substrates, i.e., compatible with industry standards. Furthermore, these GaSb-based laser diodes demonstrate low threshold current density, low optical losses, high temperature operation, and high characteristic temperatures. These results represent a breakthrough toward the integration of semiconductor laser sources on Si for smart sensors.

Hybrid Integrated Semiconductor Lasers with Silicon Nitride Feedback Circuits

Hybrid integrated semiconductor laser sources offering extremely narrow spectral linewidth, as well as compatibility for embedding into integrated photonic circuits, are of high importance for a wide range of applications. We present an overview on our recently developed hybrid-integrated diode lasers with feedback from low-loss silicon nitride (Si 3 N 4 in SiO 2 ) circuits, to provide sub-100-Hz-level intrinsic linewidths, up to 120 nm spectral coverage around a 1.55 μ m wavelength, and an output power above 100 mW. We show dual-wavelength operation, dual-gain operation, laser frequency comb generation, and present work towards realizing a visible-light hybrid integrated diode laser.

Dynamics of InAs/GaAs quantum dot lasers epitaxially grown on Ge or Si substrate

Growing semiconductor laser sources on silicon is a crucial but challenging technology for developing photonic integrated circuits (PICs). InAs/GaAs quantum dot (Qdot) lasers have successfully circumvented the mismatch problem between III–V materials and Ge or Si, and have demonstrated efficient laser emission. In this paper, we review dynamical characteristics of Qdot lasers epitaxially grown on Ge or Si, in comparison with those of Qdot lasers on native GaAs substrate. We discuss properties of linewidth broadening factor, laser noise and its sensitivity to optical feedback, intensity modulation, as well as mode locking operation. The investigation of these dynamical characteristics is beneficial for guiding the design of PICs in optical communications and optical computations.

Low-cost optical fiber physical unclonable function reader based on a digitally integrated semiconductor LiDAR.

This paper introduces an integrated fiber physical unclonable function (PUF) verification system based on a semiconductor laser source at substantially lower complexity and cost than existing alternatives. A source sub-section consisting of a linear frequency-swept semiconductor laser is used in combination with an optical frequency domain reflectometry (OFDR)/LiDAR-based measurement sub-section in order to conduct fiber identification via measurement of the unique Rayleigh reflection pattern of a section of optical fiber. When using these Rayleigh reflection patterns as PUFs, this technique results in a maximum equal error rate (EER) of 0.15% for a 5-cm section of optical fiber and an EER of less than 1% for a 4-cm section. These results demonstrate that the system can serve as a robust method fiber identification for device and communication verification applications.

The study of high-power hollow-beam laser diode

High-Power VCSEL is one of the most promising semiconductor laser sources with more advantages such as lower threshold current, compact size, efficiently fiber coupling, long lifetime compared to other types of lasers. Thanks to its slice feature, VCSEL has been the most potential light source emitting hollow laser beam. In this experiment, part of center area of P-DBRs was etched to increase the threshold of the center area of VCSEL and force carriers to gather on the edge of the VCSEL. As a result, a hollow laser beam with an output power of 350 mW and a circular optical filed distribution has been obtained.

Secure EEG Signal Transmission for Remote Health Monitoring Using Optical Chaos

For the very first time, we present the use of optical chaos for the secure transmission of electroencephalogram (EEG) signals through optical fiber medium in remote health monitoring systems. In our proposed scheme, a semiconductor laser source is used to generate optical chaos, which hides EEG signal before its transmission over the optical fiber medium. The EEG signals are acquired by using a 14-channel Emotiv headset device, which are then processed and rescaled to be compatible with the experimental environment (Optisystem). The mixing of EEG signals and chaos is performed using additive chaos masking scheme, which exhibits certain useful properties such as simplicity and easy recovery of the message. Chaotic data (a combination of EEG signals and chaos) is sent over the optical fiber medium to investigate propagation issues associated with secure EEG signal transmission. The scheme is implemented for long haul communication in which the linear impairments of optical fiber are controlled for successful transmission of the secure signal. The parameters at transmitting and receiving sides are selected to achieve synchronization, such that the transmitted signal could be subtracted from identical chaos to restore the original EEG signal at the receiving side. The scheme is tested for different lengths of the optical fiber cable in which the quality of the received signal is determined by obtaining Q-factors. This scheme could also be used with medical signals such as electrocardiography and electromyography.