Research On Thermally Tuned V-cavity Semiconductor Laser And Its Sensing Application

Since the beginning of 21st Century, the concept of "Internet of Things" has emerged customers’and businesses’need for low-cost and highly reliable optical network solutions, as well as portable and compact sensors. Tunable diode lasers, which have been enormously developed in the past decades, are building blocks in both optical networks and small-sized sensors. However, the cost, or performance of the present diode lasers are still far from practical application. Therefore, the research for a low-cost tunable diode laser with high performance is of great significance. This thesis is focused on the V-cavity laser (VCL), of which we theoretically and experimentally studied the thermally tuning, and expanded the application in methane detection and metrology.We first induced the different tuning methods of VCLs and proposed a thermally tuned VCL integrated with on-chip resistors. As an improved version, the laser succeeded in simple and compact structure and low cost in fabrication and packaging of VCLs. We designed the on-chip resistor on top of the waveguide by simulation using finite-element method (FEM), and higher tuning efficiency of the heater integrated VCL is also proved by simulation. In experiment, the laser demonstrated 28nm tuning range by single-electrode controlled digital switching and a total of 51nm tuning range with fixed temperature. The quasi-continuous tuning range is 10.8 nm with simple current controlling algorithm. The tuning efficiency is 0.136nm/mW, which is about 1.4 times higher than that in previous VCL. While the performance of both linewidth and channel switching time is improved, the heater integrated VCL also has better direct-modulation characteristics. Well-open eye diagrams with extinction ratio above 6.6dB are obtained in all channels under direct modulation at 2.5Gbps. The power penalty over 25km fiber transmission is less than 0.3dB. Clearly-open eye diagrams with bit error rates below 10"12 are also obtained at 5Gbps and 8.5Gbps after 10 km single-mode fiber transmission. With those excellent performance, the heater integrated VCL can be used as a low-cost tunable laser source for applications such as WDM access and interconnection and sensors.For gas sensing, we designed and fabricated a VCL operating around 1650nm, which can be tuned by 16nm with SMSRs around 35dB. The linewidth is lower than 500kHz. As a cheap tunable optical source, the 1650nm band VCL is capable for the methane detection.In the field of metrology, we studied the self-mixing interferometry of VCLs. By simulation using threshold equations, we investigated the feasibility of the application of self-mixing effect in VCL for measurement of velocity and displacement, and measurement of distance employing frequency-modulated continuous wave (FMCW). By using a photodiode integrated VCL, we experimentally measured the frequency and amplitude of a vibrating target. The solution is promising in the sensing market for its monolithic integration of source, detector and interferometer.