High performance optical transmitter with large bandwidth and high output power is one of the most important device in optical communications, 5th generation wireless systems and microwave photonics. We demonstrated an optical transmitter consisting of an InP-based large bandwidth travelling wave electrode (TWE) Mach-Zehnder electro-optic (EO) modulator hybrid integration with a high power distributed feedback (DFB) laser. The hybrid integration scheme was carefully designed. By using waveguide end-face coupling, the light from the InP-based DFB laser was effectively coupled into the input port of the Mach-Zehnder electro-optic modulator. A bright optical pattern at the output port of the EO modulator was observed. The output power of the integrated transmitter was measured about 0.27 mW with an inject current of 250 mA at room temperature. The transmission performance of high frequency signal was also verified by applying a microwave signal of 33 GHz. The results indicate that the simple and effective solution for hybrid integration of laser and EO modulator has potential applications in high speed optical communications.
Vertical-cavity surface-emitting lasers (VCSELs) with single-mode, single-polarization emission at a wavelength of 894.6 nm was demonstrated for miniaturized atomic clocks. Utilizing the direct-etched surface grating on the surface of VCSELs, the state of polarization of VCSELs was controlled and pinned over the whole current range. The Modal properties of VCSELs with grating structures was studied using a finite difference time domain (FDTD) method. We investigate modal loss behavior with respect to the variation of grating structural parameters for the optimization of VCSELs polarization characteristics.
In this paper, the far-field characteristic of the vertical-cavity surface-emitting laser (VCSEL) incorporating a highcontrast subwavelength grating (HCG) is analyzed by finite-difference time-domain (FDTD) method. Full three-dimensional simulations are carried out by utilizing FDTD solutions software. We study the parameters of HCG made from GaAs/AlOx which is defined by wet oxidation of an Al0.98Ga0.02As spacer layer. We have simulated HCG-VCSELs with different HCG periods and oxide aperture diameters. Various far-field patterns including single-lobe, double-lobe, triple-lobe shapes are obtained with the designed HCG-VCSEL. More interestingly, by tuning the HCG periods and the oxide aperture diameter, the far-field emission patterns transform from double-lobe to single-lobe shapes. By proper design of the two parameters, one can obtain Gaussian-like beam outputs, double-lobe or multi-lobe beams. The fullwidth half-maximum (FWHM) of the far-field divergent angle of the Gaussian-like fundamental mode obtained with grating periods of 23 and oxide aperture diameter of 8 μm is less than 5 degree. This opens a new path for engineering a VCSEL’s emission properties and provides guideline for actual device fabrication.
Deep subwavelength plasmonic graphene nanoribbon waveguides for telecommunication frequencies are proposed. The mode properties of graphene nanoribbon waveguides with varied chemical potential are numerically investigated in terms of the effective indices and the propagation length of the plasmonic modes. A refractive index as high as 4980 is obtained on the plasmonic mode along the nanoribbon waveguide with a width of 3 nm at a frequency of 190 THz, and the normalized mode area on the scale of 10−8(1/λ0)2. An embedded graphene nanoribbon waveguide was also proposed and it is that the optical characteristic can be tuned by adjusting the chemical potential of graphene. The proposed structure can be a fundamental component of the future integrated plasmonic circuit system.
We investigated the etching process especially for the integrated InGaAs/InP multiquantum-well laser. Two different
ways of etching process were demonstrated, which are RIE followed by selective wet etching and selective wet etching
only. The latter one showed ideal interface between active region and passive waveguide after regrowth. This etching
process is simpler and more effective than the first one. Using this process, we also fabricated a 1.79-μm DBR laser with
350-μm active region and 400-μm passive waveguide. The output power and threshold current and were demonstrated as
a function of temperature. The wavelength tuning characters were investigated with current and temperature changes. It
is demonstrated that this etching process can be successfully used to fabricate integrated photonic devices with
InGaAs/InP materials and the DBR laser can be a candidate for gas sensing system due to the single mode and large