This paper presents the design and fabrication of a 795 nm high-temperature single-mode single-polarization surface grating vertical-cavity surface-emitting laser. The high-temperature performance of the device was optimized using the gain-cavity mode mismatch theory, and the surface grating was designed based on rigorous coupled-wave analysis to achieve polarization control. The device exhibits excellent single-mode characteristics with a side-mode suppression ratio of approximately 35 dB. It achieves an output power of 0.89 mW at 105 degrees C, with an orthogonal polarization suppression ratio exceeding 16 dB, indicating robust polarization and temperature stability. This study successfully demonstrates a single-mode, single-polarization VCSEL operating at high temperatures up to 105 degrees C, making it suitable for applications in atomic sensing fields such as atomic clocks.

A monolithically integrated 4-channel directly modulated 1.3 μm DFB laser array has been fabricated. The device modulation bandwidth is larger than 27 GHz for all four channels. 100 Gb/s PAM4 data transmission of the device has been demonstrated.

We report the design and fabrication of a novel, to the best of our knowledge, high power 1.3 μm InGaAlAs/InP multi-quantum well (MQW) distributed feedback (DFB) laser integrated with a laterally tapered spot size converter (SSC). In the device, a section having no ridge waveguide above the MQW active material layer is introduced after the SSC section, which helps to decrease divergence angle further. The measured far field divergence angles of the laser are smaller than 10° in both lateral and vertical directions. The side mode suppression ratio (SMSR) of the laser emission is larger than 50 dB. At 50°C, the optical power is larger than 50 mW at 250 mA injection current.

Directly modulated 1.3µm InGaAlAs/InP distributed feedback (DFB) lasers having multi-quantum well (MQW) based passive distributed Bragg reflector (DBR) section have been fabricated. In the device, the DBR and DFB sections have the same MQWs, which eases the fabrication of the device by eliminating the need for additional material growth for the DBR section. Current self-heating effects on the device performance are studied by comparing two kinds of lasers having 150 and 200 µm long DFB sections, respectively. It is found that the laser with a 150 µm long DFB section has a narrower range of current within which high side mode suppression ratio (SMSR) of optical spectra can be obtained and a smaller max modulation bandwidth than the laser with a 200 µm long DFB section. This is different from a normal single-section DFB laser and can be attributed to the larger current heating effect, which shifts the emission wavelength more quickly to a long wavelength for the 150 µm device. For the 200 µm DFB length laser, a 29 GHz direct modulation bandwidth can be obtained. 50 Gb/s nonreturn to zero (NRZ) and 4-level pulse amplitude modulation (PAM4) data transmission in up to 40 km single mode fiber have been demonstrated at both room temperature and 50 °C.

We report a monolithically integrated four-channel TEML array operating in the 1.5 μm wavelength band. At 25 °C, each channel offers independent wavelength tunability with a simple tuning method, while maintaining excellent single-mode performance. The device features a bandwidth exceeding 26 GHz per channel and supports 50 Gb/s NRZ modulation, making it a simple and efficient low-cost light source for Wavelength Division Multiplexing applications.

This paper presents the design and fabrication of the single-mode 795 nm vertical cavity surface-emitting laser for high-temperature operation, which serves as the laser source of a rubidium atomic clock. The design of the structure is based on the fiber waveguide theory and the gain-mode mismatch principle, resulting in a single- mode output and stable high-temperature performance. A single-mode VCSEL was fabricated and characterized. Power-current and spectral measurements were conducted, revealing that the threshold current is 0.95 mA and the maximum output power is 1.863 mW at room temperature. At 95 degrees C, the threshold current increased to 1.11 mA, while the maximum output power decreased to 0.654 mW. The output wavelength remained at 795 nm, with a temperature drift coefficient of approximately 0.061 nm/degrees C, and the single-mode suppression ratio exceeded 30 dB. Polarization characteristics were obtained through a non-circular oxide aperture. The orthogonal polarization suppression ratio exceeded 20 dB at operating current. This study demonstrates the preparation of 795 nm VCSEL devices that operate at 95 degrees C and exhibit excellent single-mode and polarization characteristics, which lays a foundation for polarization-stabilized VCSELs with better performance.

We report an InP-based MMI combiner integrated array of 4 channel directly modulated 1.3 µm distributed feedback (DFB) lasers. Each laser channel in the array has an active DFB section and a passive distributed Bragg reflector (DBR) section. Both sections have the same InGaAlAs multi-quantum wells (MQWs) and the same grating pitch, which simplify the device design and fabrication. The 3 dB direct modulation bandwidth is larger than 28 GHz for all four channels. 25 Gb/s NRZ and 50 Gb/s PAM4 data modulations on each channel are demonstrated. The reported device is a promising low-cost monolithic light source for high capacity WDM optical communication systems.

We report a 70 GHz AlGaInAs/InP quantum-well mode-locked laser capable of producing 109 fs pulses with a spectral range spanning the C-band and L-band.

In this letter, we report transmissions of 100 Gb/s PAM4 data using a low-cost high bandwidth directly modulated 1.3 mu m distributed feedback (DFB) laser. In the device, a passive distributed Bragg reflector (DBR) section is integrated, which leads to a 29 GHz modulation bandwidth at 20 degrees C. The DFB and DBR sections of the device have the same InGaAlAs multi-quantum wells (MQWs). This simplifies the device fabrication process notably, which is similar to a conventional DFB laser. At 20 degrees C, the threshold current of the device is 14 mA and the maximum optical power for the laser is larger than 16 mW. At 100 Gb/s PAM4 data modulation, clear eye diagrams have been obtained for back-to-back and up to 40 km single mode fiber transmissions.

We report 100 Gb/s PAM4 data modulation of 1.3 μm dual wavelength DFB laser, which is a promising light source for photonics based THz communication systems.

We propose and numerically investigate a new step-ridge-waveguide InGaAlAs/InP multi-quantum well (MQW) transistor laser (TL). The carrier nonradiative recombination centers caused by the exposed deep-ridge waveguide sidewall significantly degrade the optoelectronic performance of the TLs. The step-ridge-waveguide structure guides carriers through the center portion of the ridge waveguide, thereby effectively mitigating the effect of the nonradiative recombination defects. Simulation results show that the optoelectronic characteristics of the step-ridge TL are far better than those of the conventional deep-ridge TL, and the current amplification factor of the step-ridge TL is not affected by the laser excitation. This structure provides a new option for the simultaneous enhancement of the optoelectronic performance of TLs.

A numerical calculation model of the narrow ridge waveguide was established based on the effective refrac-tive index method.The relationship between the polarization characteristics and the transverse mode of the InGaAs quantum well narrow ridge waveguide semiconductor laser was studied experimentally.According to theoretical calcula-tions,the effective refractive index difference of the TM-like mode in the ridge waveguide is larger in the direction of the slow axis.The confinement factors of the TM-like mode are larger than those of the TE-like mode,and the slow-ax-is high-order mode is more likely to appear.As the height of the ridge waveguide increases,the fast-axis high-order modes are truncated,and the confinement factor of the TE00-like mode gradually increases to be similar to that of the TM00-like mode.The slow-axis high-order mode is suppressed due to its large scattering loss,theoretically achieving high polarization,and near diffraction limit beam-quality laser output.In terms of experiments,a narrow ridge wave-guide semiconductor laser with a high polarization extinction ratio and a fundamental transverse mode was fabricated by the gain polarization characteristics of quantum well materials and by designing the height and width of the ridge.

We propose and study numerically a new deep ridge InGaAlAs/InP multi-quantum well (MQW) transistor lasers (TL), in which an n-doped InAlAs layer is inserted below the MQW layer in the device. High current gain can be obtained at the same time of laser operation, in contrast to the notable gain decreasing after lasing threshold in previous TLs. Because of the n-InAlAs layer, a normal graded index separate confinement heterostructure (GRIN-SCH) which helps to enhance the device modulation performance can be adopted. Thus, high quality electrical drivers can be expected to be integrated with high speed lasers with this InGaAlAs/InP TL structure.

We report 1.3µm InGaAlAs/InP high power DFB lasers integrated with a laterally tapered SSC, which have less than 10 degrees field divergence angle. The SMSR of the laser spectra is larger than 50 dB.

A high-power DBR-mode-locked laser diode has been demonstrated for multi-wavelength modulation. 25-Gbaud PAM4 modulation for individual comb lines is demonstrated without using an optical amplifier.

Perineuronal nets (PNNs) are important functional structures on the surface of nerve cells. Observation of PNNs usually requires dyeing or fluorescent labeling. As a network structure with a micron grid and sub-wavelength thickness but no special optical properties, quantitative phase imaging (QPI) is the only purely optical method for high-resolution imaging of PNNs. We proposed a Scattering Quantitative Interference Imaging (SQII) method which measures the geometric rather than transmission or reflection phase during the scattering process to visualize PNNs. Different from QIP methods, SQII method is sensitive to scattering and not affected by wavelength changes. Via geometric phase shifting method, we simplify the phase shift operation. The SQII method not only focuses on interference phase, but also on the interference contrast. The singularity points and phase lines of the scattering geometric phase depict the edges of the network structure and can be found at the valley area of the interference contrast parameter SINDR under different wavelengths. Our SQII method has its unique imaging properties, is very simple and easy to implement and has more worth for promotion.

We report the fabrication of a first electro-absorption modulated widely tunable DBR lasers (TEML) based on InGaAlAs multi-quantum well (MQW) material, which is superior than InGaAsP MQWs for the fabrication of both modulators and lasers. The device is fabricated by using butt-joint material growth technology and operates at a wavelength of 1.5 mu m. An over 12 nm wavelength tuning range can be obtained. The characteristic temperature of the device is 83 K, which is notably higher than that for a laser based on InGaAsP MQWs. At 25 degrees, the electro-absorption modulator (EAM) of the device has a small signal modulation bandwidth exceeding 27 GHz, which is notably higher than the bandwidth for a TEML device having the same structure but InGaAsP MQW active material. At 25 Gb/s NRZ data modulation, to achieve 10E-10 bit error rate (BER), the power penalty after 5 and 10 km fiber transmission are 1 and 3 dB, respectively. The device is a promising low-cost light source for future high-capacity wavelength division multiplexing (WDM) optical communication systems.

In this letter, we report the fabrication of Uni-travelling-carrier photodiode (UTC-PDs) for mm-wave applications. For the fabricated PDs, the area of the p electrode is smaller than that of the absorption area. Though this leads to a response roll off when the frequency is below 3.5 GHz, a higher impedance of the PD can be obtained, which leads to a higher RF power output for a 50 Omega load resistance. For the PD having 50 x 4 mu m(2) absorption area and 46 x 2.5 mu m(2) p electrode area, the measured RF output power at 6 mA photocurrent, -2V bias and 15 GHz is 0.2 dBm. The ideal RF output power for a PD at this current is 0.35 dBm, which is only 0.15 dB higher than the measured RF power, indicating a high RF power output efficiency.

In this paper, we present a novel, to our knowledge, method for the fabrication of slotted surface gratings for buried heterostructure (BH) lasers. In the device fabrication process, SiO2 strips needed for InP current blocking layer growth are reused for the formation of slot grating pattern masks. In the following growth of the p-InP cladding layer, because the slot areas are covered by SiO2, the InP material is grown selectively in only the areas outside the slot areas, forming slots of the surface gratings in the p-InP layer at the same time as the cladding layer growth. Single longitude mode BH lasers having slotted surface gratings have been fabricated successfully, and the spectra show higher than 40 dB side mode suppression ratio (SMSR). The adoption of the method helps to simply the device fabrication and thus lower the device fabrication cost notably.

1.5 µm wavelength high power buried heterojunction (BH) semiconductor lasers having dilute waveguide structure have been fabricated. The optical field is dragged down toward the n side of the device by the dilute waveguide layer, lowering the optical confinement factor of the p doped material and active material, which helps to enlarge the laser output light power. Compared with thick InGaAsP cladding layer, the dilute waveguide material is easy to be grown and has higher thermal conductivity. The slope efficiency of the obtained dilute waveguide BH lasers is notably higher than that of the BH lasers having no dilute waveguide. Our studies show that the dilute waveguide structure is promising for the fabrication of high power BH lasers.