Wavelength Tunable Laser Diode Research Articles

Optimization of the coupling efficiency under self-injection locking in a narrow linewidth hybrid wavelength tunable laser diode

In this study, a fiber Fabry–Perot (FFP) interferometer was connected to a hybrid wavelength-tunable laser diode consisting of a semiconductor optical amplifier chip and Si photonics chip, and spectral linewidth narrowing was achieved using the self-injection locking effect. The hybrid wavelength-tunable laser was equipped with a variable-reflectivity mirror, which allowed the optimization of κ, the coupling efficiency between the laser cavity and FFP interferometer. By optimizing κ, self-injection locking stabilized, and the linewidth was controlled between 4 and 300 kHz. This laser can be used to evaluate the linewidth required for communication systems such as digital coherent communication and the accuracy required for distance measurement.

Silicon-based high-resolution and low-power-consumption two-dimensional beam scanner integrated with hybrid wavelength-tunable laser diode

Optical phased array (OPA) is a useful device for achieving the solid-state beam scanner required in compact light detection and ranging. However, conventional OPAs actively control the phase difference between arrays. Therefore, power consumption is extremely high in a high-resolution OPA. Herein, we fabricated a passive OPA with a 128-channel silicon arrayed waveguide and Si-dot grating antennas with large apertures. Moreover, we integrated a hybrid wavelength-tunable laser diode with a passive OPA. The field of view was 43.9° × 10.4°, and the FWHM of the beam width was 0.233° × 0.0495°. The power consumption per antenna was 0.397 mW.

Optical injection locking and optical-fiber data transmission by directly modulated wavelength tunable laser transmitters

Enhancement of the small- and large-signal modulation performance of wavelength tunable laser diode (TLD) transmitters under strong optical injection locking (OIL) is investigated numerically in back-to-back and optical-fiber transmission schemes. Our model is based on the spatiotemporal description of laser dynamics as due to the composite cavity design of TLDs, the usual rate equation formalism is not directly applicable. We demonstrate that TLD transmission strongly depends on wavelength tuning, which was investigated over a 21-nm range between 1529 and 1550 nm emission wavelengths. The best performance for both free-running (FR) and OIL TLDs is achieved at shorter wavelengths, 1529 nm for our device. Although in both cases this is due to larger differential material gain at shorter wavelengths, the underlying physics of the effect is completely different. For an FR TLD, it is the resonance oscillation frequency (ROF) that defines the best modulation speed, while for an OIL TLD, the achievable modulation speed depends on the cavity mode shift due to optical injection. Both the ROF and the cavity mode shift increase when the differential gain increases. However, the ROF is the device’s fixed parameter, while the cavity mode shift is defined by the OIL conditions, and thus, it can be optimized. The superior performance of the optical fiber digital data transmission with the OIL TLD is demonstrated at around 20-Gb/s modulation speed for standard fibers. This result is attributed to an enhanced modulation response and suppressed frequency chirping of the OIL TLD, and it is important for practical utilization of TLD transmitters.

Silicon photonics hybrid wavelength tunable laser diode using curved directional couplers with 145 nm tunable range

The expansion of the wavelength tunable range of wavelength tunable laser diodes is required in optical communication and sensing. Curved directional couplers (DCs) exhibit smaller power coupling efficiency fluctuations than conventional straight DCs, which reduces the wavelength sensitivity of double-ring wavelength filters. In this study, we fabricated a hybrid wavelength tunable laser diode comprising curved DCs with an improved design. This laser diode had a wavelength tunable range of 145.2 nm, which is the broadest tunable range as an external-cavity laser diode with silicon waveguides.

Hybrid laser diode with ultrawide wavelength-tunable range using curved directional couplers.

Wavelength-tunable laser diode with a wide tuning range is required for optical communication systems and optical sensing. External cavity laser diodes with silicon-photonic wire waveguides and ring resonators have small footprint because of high refractive index contrast between Si. However, power coupling efficiency κ of conventional straight directional coupler between ring and bus waveguides have large wavelength dependence, which lowers tunable range. In this study, we demonstrate a hybrid wavelength-tunable laser diode using curved directional couplers, whose wavelength dependence on κ is low. The wavelength-tunable range record of 120.9 nm has been achieved. In addition, curved directional couplers are tolerant of waveguide width fabrication error.

Compact and Low Power-Consumption Solid-State Two-Dimensional Beam Scanner Integrating a Passive Optical Phased Array and Hybrid Wavelength-Tunable Laser Diode

Large-scale optical phased arrays have attracted attention as devices for solid-state beam scanning employing light detection and ranging. However, conventional optical phased arrays using electro-optic phase shifters require active phase control for each antenna. Because the power consumption of the active phase shifters is proportional to the number of antennas, the total power consumption increases in a large-scale optical phased array with a narrow beam divergence. In this study, we propose a passive beam scanner that realizes two-dimensional beam scanning through the wavelength sweep of a laser light. Additionally, most studies on optical phased arrays use external laser diodes as light sources. This increases the size of the beam-scanning system. Therefore, there is a demand for integrating an optical phased array and a laser light source in a combined chip. In this study, we integrated a 64-channel passive optical phased array and a hybrid wavelength-tunable laser diode into a combined chip. The size of the device was 5 mm × 1.5 mm, and the power consumption for beam scanning was 49.3 mW. The field of view was 44.2° × 13.7°, and the full width at half maximum of the beam divergence was 0.517° × 3.67°. Compared with the device used in a previous study, our device was nine times smaller, and the total power consumption was only tens of milliwatts. This device consumes less power and achieves a fully integrated light detection and ranging.

Toward Nonepitaxial Laser Diodes.

Thin-film organic, colloidal quantum dot, and metal halide perovskite semiconductors are all being pursued in the quest for a wavelength-tunable diode laser technology that does not require epitaxial growth on a traditional semiconductor substrate. Despite promising demonstrations of efficient light-emitting diodes and low-threshold optically pumped lasing in each case, there are still fundamental and practical barriers that must be overcome to reliably achieve injection lasing. This review outlines the historical development and recent advances of each material system on the path to a diode laser. Common challenges in resonator design, electrical injection, and heat dissipation are highlighted, as well as the different optical gain physics that make each system unique. The evidence to date suggests that continued progress for organic and colloidal quantum dot laser diodes will likely hinge on the development of new materials or indirect pumping schemes, while improvements in device architecture and film processing are most critical for perovskite lasers. In all cases, systematic progress will require methods that can quantify how close new devices get with respect to their electrical lasing thresholds. We conclude by discussing the current status of nonepitaxial laser diodes in the historical context of their epitaxial counterparts, which suggests that there is reason to be optimistic for the future.

Wavelength-Tunable Narrow-Linewidth Laser Diode Based on Self-Injection Locking with a High-Q Lithium Niobate Microring Resonator.

We demonstrate a narrow linewidth 980 nm laser by self-injection locking of an electrically pumped distributed-feedback (DFB) laser diode to a high quality (Q) factor (>105) lithium niobate (LN) microring resonator. The lithium niobate microring resonator is fabricated by photolithography-assisted chemo-mechanical etching (PLACE) technique, and the Q factor of lithium niobate microring is measured as high as 6.91 × 105. The linewidth of the multimode 980 nm laser diode, which is ~2 nm measured from its output end, is narrowed down to 35 pm with a single-mode characteristic after coupling with the high-Q LN microring resonator. The output power of the narrow-linewidth microlaser is about 4.27 mW, and the wavelength tuning range reaches 2.57 nm. This work explores a hybrid integrated narrow linewidth 980 nm laser that has potential applications in high-efficient pump laser, optical tweezers, quantum information, as well as chip-based precision spectroscopy and metrology.

Simple high-precision diode laser system with digital control.

A simple wavelength tunable diode laser system has been designed and fabricated for laboratory use. Both the current and temperature controllers are based on an AVR microcontroller, and the experimental controls have been implemented with the help of daemon programs running in a message passing interface environment, which allows the users to run the control server and client programs on separate computers. The stability of the controllers has been tested using a distributed feedback (DFB) diode laser with a central wavelength of 852.3nm. A noise spectral analysis of the current controller with and without the use of the diode laser as the active load has been demonstrated. The absorption spectra of 6S 1/2→6P 3/2 transition of 133 C s, as recorded by using the DFB laser system developed, are also presented.

Sub-kHz linewidth, hybrid III-V/silicon wavelength-tunable laser diode operating at the application-rich 1647-1690 nm.

The wavelength region about of 1650 nm enables pervasive applications. Some instances include methane spectroscopy, free-space/fiber communications, LIDAR, gas sensing (i.e. C2H2, C2H4, C3H8), surgery and medical diagnostics. In this work, through the hybrid integration between an III-V optical amplifier and an extended, low-loss wavelength tunable silicon Vernier cavity, we report for the first time, a III-V/silicon hybrid wavelength-tunable laser covering the application-rich wavelength region of 1647-1690 nm. Room-temperature continuous wave operation is achieved with an output power of up to 31.1 mW, corresponding to a maximum side-mode suppression ratio of 46.01 dB. The laser is ultra-coherent, with an estimated linewidth of 0.7 kHz, characterized by integrating a 35 km-long recirculating fiber loop into the delayed self-heterodyne interferometer setup. The laser linewidth is amongst the lowest in hybrid/heterogeneous III-V/silicon lasers.

Incoherent Laser Heterodyned Long-Reach 60-GHz MMWoF Link With Volterra Filtered 16-QAM OFDM Beyond 13 Gbps

By remotely heterodyning two independent laser carriers, the long-reach 60-GHz millimeter-wave-over-fiber (MMWoF) link is demonstrated for the Volterra series filtered quadrature amplitude modulation orthogonal frequency division multiplexing (QAM-OFDM) transmission with nonlinear noise suppression, which enables 13-Gbps data delivery through 50-km single-mode fiber (SMF) and 3-m free-space links. A wavelength tunable colorless laser diode transmits the Volterra filter equalized QAM-OFDM data to remotely couple with a localized single-mode laser carrier at the optical receiving end of the MMWoF system. Such an incoherently coupled dual-mode carrier facilitates the optical single-carrier modulation to suppress chromatic dispersion induced power fading effect of the SMF transmitted QAM-OFDM data. The 2nd+3rd-order nonlinear noise induced by direct modulation, heterodyne conversion, and phase fluctuation of the incoherently coupled dual-mode carrier is corrected with the Volterra filter equalization to upgrade the decoded signal-to-noise ratio (SNR) by >2 dB. After remotely heterodyning the downstream and the localized carriers with mutual incoherence in between, the 16-QAM OFDM transmission at a data rate up to 13.2 Gbps is successfully delivered over 3-m wireless link, which reveals the FEC certificated error vector magnitude of 14.1%, SNR of 17 dB, and bit error rate of 1.7 × 10−3.

Compact silicon photonic hybrid ring external cavity (SHREC)/InGaSb-AlGaAsSb wavelength-tunable laser diode operating from 1881-1947 nm.

In recent years, the 2 µm waveband has been gaining significant attention due to its potential in the realization of several key technologies, specifically, future long-haul optical communications near the 1.9 µm wavelength region. In this work, we present a hybrid silicon photonic wavelength-tunable diode laser with an operating range of 1881-1947 nm (66 nm) for the first time, providing good compatibility with the hollow-core photonic bandgap fiber and thulium-doped fiber amplifier. Room-temperature continuous-wave operation was achieved with a favorable on-chip output power of 28 mW. Stable single-mode lasing was observed with side-mode suppression ratio up to 35 dB. Besides the abovementioned potential applications, the demonstrated wavelength region will find critical purpose in H2O spectroscopic sensing, optical logic, signal processing as well as enabling the strong optical Kerr effect on Si.

Millimeter-Wave Radio-Over-Fiber Network for Linear Cell Systems

We discuss and propose millimeter-wave linear cell systems for signal distribution on railway radiocommunication systems between train and trackside, and a foreign object debris detection system for airport runways using the radio-over-fiber network technology. Linear cell configurations based on wavelength-division multiplexing (WDM) and power-splitter-based distribution networks are discussed and demonstrated experimentally. A single-sideband modulation for data transmission in an intermediate frequency over a fiber system is successfully transmitted with an ultrafast wavelength-tunable laser diode for WDM routing to track the train car within 3 $\mu$ s. Radar signal distribution by an optical double-sideband suppressed-carrier modulation mitigates the dispersion effect of the fiber cable to transmit a 32-GHz signal into the remote radar heads.

1.5μm, mode-hop-free full C-band wavelength tunable laser diode with a linewidth of 8 kHz and a RIN of -130 dB/Hz and its extension to the L-band.

We demonstrate a narrow-linewidth, low-intensity noise, widely wavelength-tunable LD for which we adopted a long external cavity configuration (ECLD) with a tunable optical filter. By employing a simultaneous tuning circuit between the optical filter and the Fabry-Perot mode caused by the external cavity, the oscillation wavelength was successfully tuned over the full C-band without mode hopping. The tunable optical filter bandwidth was 0.55 nm (1530~1570 nm). We achieved a linewidth of less than 8 kHz obtained with a delayed self-heterodyne method. On the other hand, the linewidth estimated from the white noise level of the optical frequency modulation noise power spectrum of the laser output was as narrow as 314 Hz. A relative intensity noise (RIN) below -130 dB/Hz was simultaneously achieved over the C-band range. With the same configuration except for an optical filter with a filter bandwidth of 0.6 nm for L-band operation (1570~1610 nm), we also realized a full L-band wavelength tunable ECLD with a linewidth of less than 7.7 kHz and a RIN of below -126 dB/Hz.

Narrow Spectral Linewidth Silicon Photonic Wavelength Tunable Laser Diode for Digital Coherent Communication System

We demonstrated wavelength tunable laser diodes with Si-wire waveguide ring resonators as an external optical cavity. The footprint of the optical cavity including the semiconductor optical amplifier is as small as 0.8 mm × 0.6 mm which is less 1/10 of those made of silicon oxinitride material. Wavelength tuning range of approximately 55 nm was demonstrated, which covers entire L-band of the optical communication wavelength system. Furthermore, a spectral linewidth narrower than 100 kHz was obtained by optimizing the design of the external optical cavity. The optical nonlinearity of silicon is described and the influence on laser oscillation is also discussed.

Heterogeneous quantum dot/silicon photonics-based wavelength-tunable laser diode with a 44 nm wavelength-tuning range

A heterogeneous wavelength-tunable laser diode combining quantum dot and silicon photonics technologies is proposed. A compact wavelength-tunable filter with two ring resonators was carefully designed and fabricated using silicon photonics technology. The tunable laser combining the wavelength-tunable filter and an optical amplifier, which includes InAs quantum dots, achieved a 44.0 nm wavelength-tuning range at around 1250 nm. The broadband optical gain of the quantum dot optical amplifier was effectively used by the optimized wavelength-tunable filter. This heterogeneous wavelength-tunable laser diode could become a breakthrough technology for high-capacity data transmission systems.

Ultra-compact wavelength-tunable quantum-dot laser with silicon-photonics double ring filter

Compact, wavelength-tunable light sources are desired for the enhancement of information communication technology and bio-imaging applications. We propose a compact, wavelength-tunable laser diode with a wide wavelength-tunable range around 1230 nm consisting of a quantum-dot optical amplifier and a silicon photonic tunable filter. High-quality InAs quantum dots grown with the sandwiched sub-nano separator technique were used as the optical gain medium. The wavelength-tunable filter was constructed with ring resonators fabricated using silicon photonics. The single-mode laser oscillation was demonstrated with a 28.5-nm wavelength-tunable range.

Compact silicon photonic wavelength-tunable laser diode with ultra-wide wavelength tuning range

We present a wavelength-tunable laser diode with a 99-nm-wide wavelength tuning range. It has a compact wavelength-tunable filter with high wavelength selectivity fabricated using silicon photonics technology. The silicon photonic wavelength-tunable filter with wide wavelength tuning range was realized using two ring resonators and an asymmetric Mach-Zehnder interferometer. The wavelength-tunable laser diode fabricated by butt-joining a silicon photonic filter and semiconductor optical amplifier shows stable single-mode operation over a wide wavelength range.

Hybrid mode-locked Er-fiber oscillator with a wide repetition rate stabilization range

We present a hybrid mode-locked Er-fiber oscillator whose repetition rate can be tuned from 101.3 to 103.0 MHz. By incorporating saturable absorption and nonlinear polarization evolution in a ring cavity, mode-locked states can be easily accessed with a 3 dB spectral range wider than 50 nm. In addition, by the combination of a computer-controlled optical delay line and a piezo actuator to change the length of the cavity, the repetition rate can be stabilized at any frequency in the tunable range for the long term. When phase locking to an Rb clock for 14 h continuously, the standard deviation of the fundamental repetition rate is 0.2 mHz with a gate time of 1 s. In addition, the feedback bandwidth can be extended to ∼400 Hz by stabilizing the 10th harmonic instead of the fundamental repetition rate. Furthermore, the linewidth of the comb modes is investigated by beating with a wavelength-tunable diode laser.

Silicon Photonic Wavelength-Tunable Laser Diode With Asymmetric Mach–Zehnder Interferometer

We fabricated wavelength-tunable laser diodes using a Si photonic wavelength filter that consists of ring resonators and an asymmetric Mach-Zehnder interferometer. The footprint of the optical cavity including the semiconductor optical amplifier is small, 2.6 mm × 0.5 mm, which is about 1/9 of those for tunable laser diodes made of silicon oxynitride. The wavelength could be tuned over approximately 62 nm, which covers the entire L-band of the optical communication wavelength range. The maximum output power reaches 42.2 mW. Furthermore, a spectral line width narrower than 100 kHz was obtained. Such tunable laser diodes with narrow spectral line widths are suitable as light sources integrated into other digital coherent devices.