The operation of the device is affected by the increase in temperature caused by the rough electrodes surface of the thinfilm lithium niobate modulator. We have developed simulation models to analyze the relationship between roughness and maximum surface temperature of gold electrodes and to examine the influence of snowball radius and surface area ratio on the maximum surface temperature. The results indicate that both surface area ratio and snowball radius affect maximum surface temperature change, with the influence of surface area ratio being greater than that of snowball radius within the range of 2-6nm and a surface area ratio between 1.6-2.5, respectively.
A 16-channel optical transmitter chip with a digital transmission capacity up to 1.6 Tb/s has been demonstrated. In this chip, a 16-wavelength III–V DFB laser array (MLA), a silicon Mach-Zehnder interferometer (MZI) modulator array and a 16-channel fiber array are hybrid integrated by photonic wire bonding (PWB) technique. The MLA based on reconstruction-equivalent-chirp (REC) technique proves a good wavelength spacing uniformity of all wavelengths. Each unit laser with 1.2 mm cavity length in the MLA exhibits good single-longitudinal-mode operation with the output power over 18 dBm at an injection current of 300 mA. Spectral measurements show the channels coincide well with the designed 200 GHz spacing, with wavelength deviations within a range of ±0.2 nm. Based on PWB technique, three chips mentioned above are integrated optically on one Wu-Cu substrate as a 16-channel optical transmitter. The largest output power of optical transmitter is 1.5 mW and all channels still keep good single mode outputs after PWB integration. The tested modulation speed of each channel is up to 100 Gb/s, which implies the total transmission capacity of this device is 1.6 Tb/s.
KEYWORDS: Waveguides, Distributed feedback semiconductor lasers, Design and modelling, Continuous wave operation, High power lasers, Laser development, Semiconductor lasers, Optical simulations, Near field
In this paper, we designed a Slab Coupled Optical Waveguide (SCOW) DFB semiconductor laser around 1550 nm with increased output optical power and single mode operation. Under the assumption of idea heat dissipation, we simulate the performances of the designed DFB laser using PICs3D software. A Continuous-Wave (CW) output power of 1.03 W is obtained under the bias current of 2.7A, with the slope efficiency of 0.402 W/A. Because of the asymmetric Separated Confinement Heterostructure (SCH) and the passive waveguide structure, the mode profile is expanded. Then, single mode outputs with near-field mode spot size of 5 μm×5 μm and the Full Width at Half Maximum (FWHM) far-field divergence angle is as low as 9.2°×16.2°. Therefore, the designed 1550 nm high power DFB semiconductor laser has potential applications in the fields such as silicon-based photonics integration, Free Space Optical (FSO) communication and light detection and ranging (LiDAR) systems.
As a key link in the practical application of optical modules, the packaging technology of optoelectronic devices plays a crucial role in the performance of products. Among them, the optical coupling technology is an important link in the packaging design process, and the lensed fiber coupling method still occupies a large proportion in the packaging technology due to its simple structure and low cost. In this paper, by adjusting the parameters of the taper angle and curvature radius of the lensed fiber, a simulation model of the optical coupling between the lensed fiber and commercial lasers is established, and the optical coupling efficiency and optical tolerance of the lensed fiber under different horizontal coupling distances and angular offsets are analyzed in detail. In addition, the coupling performance of the lensed fiber with two different manufacturing processes, the ground- cone lensed fiber (GCLF) and the fused-cone lensed fiber (FCLF), was compared and analyzed. According to the comparative analysis results, under the optimal parameters, the maximum coupling efficiency of GCLF reaches 89.35%, and the maximum coupling efficiency of FCLF reaches 85.59%. By adjusting the alignment angle of the laser light source in the horizontal and vertical directions, the 3db alignment tolerances of GCLF in two directions are 2.17μm and 2.05μm, respectively, and the 3db alignment tolerances of FCLF in two directions are 2.08μm and 1.96μm, respectively. From this, it can be seen that GCLF has higher coupling performance than FCLF, and a higher alignment tolerance during the package alignment process.
We have experimentally demonstrated a 16-wavelength high-power DFB laser array with 200 GHz (1.6 nm) channel spacing based on the asymmetric equivalent π phase shift. Good single-longitudinal-mode (SLM) operations are obtained by introducing asymmetric equivalent π phase shifts. The effect of random phase on the high-reflective (HR) coating facet also is weakened by introducing asymmetric equivalent π phase shifts which are implemented at the 1/5 laser cavity close to the facet with HR coating. The average channel spacing is 1.62 nm, which deviated 0.02 nm from our design under the same injection current (300 mA) of each laser. The output power of 16 channels is above 100 mW at the bias current of 400 mA and the average slope efficiency is 0.41 W/A at 25 °C. Good single-longitudinal-mode are obtained for all the 16 channels with side mode suppression ratios of above 50 dB. Besides, the relative intensity noise at an injection current of 200 mA is below -157 dB/Hz.
As one of the most important applications of microwave photonic,ROF (Radio over Fiber) system,which combines the advantages of optical communication and wireless communication,is a good candidate for broadband mobile Communication In this paper, we built and simulation a 60GHz RoF(Radio-over-Fiber) transmission system based on PM modulator. First, we introduce the PM-IM(Phase modulation to intensity modulation) modulation mechanisms by the breaking the phase balanced approach. This method solves the problem that the constant envelope (phase modulation signal) generated by the phase modulator can not be directly detected by a photo detector. A standard single-mode fiber (SMF) is connected input to the F-P(Fabry-Perot) optical filter, which is to achieve the PM-IM modulation conversion by changing the wavelength of the laser or the frequency of the modulation factor of the F-P optical filter to adapt to different fiber lengths and the signal transmission rate. These two methods which changing the phase relationship between the optical carrier and the optical side band can realize the ideal phase transition to obtain efficient and low loss modulation conversion. Finally, the simulation results show that different fiber lengths and the signal transmission rate configuration of different wavelength of the laser or the frequency of the modulation factor of the F-P optical filter, the BER performance and the eye diagram of the 60GHz RoF transmission system signals have been improved based on these PM-IM modulation methods.
A high-speed DFB laser module in butterfly housing has been fabricated in our laboratory, which is operated in direct
modulation for Ku-band. The bandwidth of the laser module is measured up to 18 GHz with highly linear characteristics
and low relative intensity noise. The input points for 1 dB compression and third order interception of the laser have also
been obtained as 23 dBm and 30 dBm respectively, and it can be utilized in analog optical link systems with good
performance.
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