Dual-wavelength Semiconductor Laser Research Articles

A Stable Dual-Wavelength DFB Semiconductor Laser With Equivalent Chirped Sampled Grating

A monolithic integrated dual-wavelength DFB semiconductor laser is fabricated and experimentally demonstrated. Utilizing the reconstruction-equivalent chirp (REC) technique, dual-wavelength lasing is obtained by introducing two symmetric equivalent phase shifts in a chirped sampled Bragg grating. The laser operates at 1650 nm and the wavelength spacing is about 0.8 nm at room temperature. The frequency of the beat signal between the two wavelengths is 88.47 GHz, and the linewidth of the beat signal is 5.1 MHz. Based on the REC technique, the grating pattern can be fabricated by using holographic exposure combining with conventional lithography. This work provides a simple and cost-effective way to achieve dual-wavelength semiconductor laser.

Effects of Photobiomodulation on High Glucose Induced Oxidative Stress in Human Embryonic Skin Fibroblasts

In this study, we explored the effects of photobiomodulation (PBM) on the functional damage of human embryonic skin fibroblasts (CCC-ESFs) in a high glucose environment, as well as the effects of PBM on tissue repair, to provide a theoretical basis for application and promotion of dual-wavelength laser therapy in clinical practices. CCC-ESFs were cultured in vitro for 2 d in a high glucose medium, and then irradiated with a 635/808 nm dual-wavelength semiconductor laser at a dose of 20 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , 0-24 J/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Cell proliferation, reactive oxygen species (ROS) production, antioxidant enzyme activity (CAT, SOD), lipid oxidization capacity (MDA), cell growth factors, and the expression of matrix metalloproteinases (MMPs) and matrix metalloproteinase inhibitors (TIMPs) were assessed. We found that PBM can enhance the proliferation of fibroblasts, improve the inhibitory effects of the high glucose environment on cell proliferation, increase intracellular ROS production, enhance the activity of antioxidant enzymes, and stimulate cytokine secretion. Furthermore, PBM was found to inhibit the expression of MMPs, increase the expression of TIMPs, reverse the overexpression of MMPs/TIMPs caused by high glucose, and promote wound healing.

A Monolithic Integrated Dual-Wavelength DFB Laser With Equivalent Inverse-Gaussian Apodized Grating

A monolithic integrated dual-wavelength DFB laser with inverse-Gaussian apodized sampled Bragg grating (IGASBG) is proposed and investigated. The IGASBG in the DFB laser is achieved by varying the duty cycle of sampled Bragg grating. The frequency spacing between the two lasing modes can be designed from 38 GHz to 660 GHz which covers almost the entire millimeter-wave range and reaches terahertz. The results proposed in this paper have great reference value for fabricating dual-wavelength semiconductor lasers.

Double microring resonator coupled dual-wavelength semiconductor lasers

A novel monolithically integrated double microring resonator coupled dual-wavelength semiconductor laser is proposed. Two microring resonators incorporated in the laser cavity are used as the strong mode-selection filters to select the resonance modes by vernier effect and the equivalent reflective mirrors to form the traveling-wave cavity. A cleavage-free traveling-wave laser cavity replaces the standing-wave FP cavity formed by cleaved reflective facets. Theoretical simulations show that, compared to standing-wave supported structures, traveling-wave structure double microring coupled laser offers many promising advantages, including simple fabrication, reasonably low threshold current of about 34 mA and good side-mode suppression ratio (SMSR) of over 31 dB. The new design can provide dual wavelength lasing with excellent uniformity and stability as the gain peak of the active region and the resonance modes distribution are controlled properly.

Dual-wavelength semiconductor laser array with two asymmetric equivalent distributed phase shifts

A dual-wavelength laser array is obtained by two asymmetric phase shifts. Different wavelength spacings are obtained by varying the magnitude of the phase shifts. The phase shifts are distributed along two phase-arranging regions, which are obtained equivalently by specially-designed sampled structures with uniform seed gratings.

Dual Wavelength Semiconductor Laser Based on Reconstruction-Equivalent-Chirp Technique

A novel dual wavelength semiconductor laser is proposed and experimentally demonstrated. Stable dual wavelength lasing is established by the grating structure consisting of two asymmetric phase-shifts, which are distributed along the phase-arranging regions in the sampling pattern. The wavelength spacing between the two modes is about 0.51 nm at room temperature. A microwave signal at about 64 GHz can be generated by beating the two wavelengths. Based on the reconstruction-equivalent-chirp technique, the laser is fabricated by a low-cost manufacturing method.

95 GHz millimeter wave signal generation using an arrayed waveguide grating dual wavelength semiconductor laser

We report the generation of a 95 GHz carrier frequency by optical heterodyning of two wavelengths from adjacent channels from an arrayed waveguide grating-based multiwavelength laser. The extended cavity structure of the device provides low phase noise and narrow optical linewidth, further enhanced by the intracavity filter effect of the arrayed waveguide grating. We demonstrate that the generated RF beat note, at 95 GHz, has a -3 dB linewidth of 250 kHz. To the best of our knowledge, this is the narrowest RF linewidth generated from a free-running dual-wavelength semiconductor laser. The device is realized as a photonic integrated circuit using active-passive integration technology, and fabricated on a multiproject wafer run, constituting a novel approach for a compact, low-cost dual-wavelength heterodyne source.

Mode competition analysis in dual-wavelength coupled-cavity semiconductor laser

The mode competition in a dual-wavelength quarter-wave coupled-cavity semiconductor laser is analyzed using Langevin noise-driven rate equations. The laser can achieve simultaneous emission of two optical modes as a doublet with the same threshold, while the frequency difference of the two lasing wavelengths can be tuned by the injection currents. The analytical expressions for the spectral positions of the doublet and the threshold gain are derived, and a numerical model based on Langevin noise-driven rate equations is established for the mode competition process with enhanced physical insight.

Electrically Tunable and Dual-Wavelength Semiconductor Laser with a Liquid Crystal Display

An electrically tunable semiconductor laser with a liquid crystal display (LCD) and a commercially available laser diode is presented. We tested two types of LCD under strong laser light and, on the basis of the results, selected the supertwist-nematic (STN) LCD with a passive matrix. Tuning is achieved up to 5 nm by moving a single stripe pattern displayed on the LCD. The wavelength shifts in 0.553 nm/cell, which agrees well with the calculated resolution derived from the diffraction grating formula. Dual-wavelength oscillation is also achieved up to a wavelength separation of 4.62 nm using the double stripe pattern.

Experimental study of nonlinear mode mixing in dual-wavelength semiconductor lasers

New schemes for the generation of the sum, difference, and double frequencies in dual-wavelength injection lasers, based on an intracavity nonlinear mode mixing owing to a bulk nonlinearity, are experimentally investigated. Namely, the operation of the dual-wavelength laser diodes at the TE0 and TE1 modes, butt-joint laser diodes, and interband cascade lasers with tunnel junction are described.

Nonlinear mode mixing in dual-wavelength semiconductor lasers with tunnel junctions

The authors demonstrate and study two- and three-wavelength generations in the semiconductor diode laser with a tunnel junction separating two different quantum-well active regions integrated within a single waveguide. To avoid resonant cross absorption of the modes at different frequencies and achieve phase matching, the laser waveguide is designed to generate the first-order transverse mode at a longer wavelength and the third-order mode at a shorter wavelength. Excellent agreement with the designed and measured device parameters is observed. Intracavity nonlinear mixing leading to sum-frequency and second-harmonic generation is demonstrated.

Investigation of laser-mode anticompetition in semiconductor lasers

Influential factors of laser-mode anticompetition are investigated in dual-wavelength semiconductor laser. Experiment shows that with increasing wavelength, separation, or decreasing initial power of the long-wavelength mode (LWM), the slope of the anticompetition curve and the maximum power increment of the LWM increase. Under fixed wavelength separation, anticompetition can exist only when the power of the short-wavelength mode (SWM) is below a certain level. In addition, the wavelength position has an effect on anticompetition. Different injection current also results in different behaviors of anticompetition. Anticompetition can only be observed with varying the power of the SWM.

174-nm Mode Spacing in Dual-Wavelength Semiconductor Laser Using Nonidentical InGaAsP Quantum Wells

A very wide tuning range of dual-wavelength semiconductor lasers with properly designed nonidentical InGaAsP quantum wells is reported. As the external cavity of reflected-type grating telescope configuration is well aligned, the dual-wavelength operation can be achieved with a record wavelength separation as large as 174 nm (25 THz). The wide separation of two wavelengths is possible due to a proper modification of the external-cavity configuration and reduced gain competition of laser modes.

Characteristics of a dual-wavelength semiconductor laser near 1550 nm

The implementation of a widely tunable, dual-wavelength semiconductor laser near 1550 nm is reported. The characteristics of its operation under different conditions of injection current and output feedback are discussed. Because the gain spectrum of this laser varied significantly with the injection current level, the signals of the two oscillating wavelengths interplay through the competition for the carriers. Generally, the feedback of the signal of one wavelength enhanced its own output power and suppressed the other unless the gain of the former is significantly lower than the later.

Wide-range tunable dual-wavelength semiconductor laser using asymmetric dual quantum wells

Using asymmetric dual quantum wells for the laser material, the semiconductor laser is able to operate at dual wavelengths with an extremely wide tuning range. The spectral spacing could be tuned to as large as 55.7 mn (25 THz). With the spectral spacing fixed, the two wavelengths could also be simultaneously tuned for a range as wide as 34.7 nm. In addition, with one wavelength fixed, the other one could be separately tuned. The experiments indicate that the two wavelengths can be almost randomly selected within a large spectral range over 30 nm.

Carrier capture competition between two different quantum wells in dual-wavelength semiconductor lasers

Based on a three-level model, we have numerically shown that a semiconductor gain medium with a structure consisting of two different quantum wells may lead to dual-wavelength laser operation if the balance of carrier capture competition between the two wells can be reached. The major controlling parameters for the operation are the ratio of the carrier quantum capture times of the two wells and the absorption constant of the short-wavelength photons by the long-wavelength quantum well. It is shown that there exists a large parameter space for dual-wavelength operation.