Research On Emission Wavelenght And Threshold Characteristics Of Coupled-Cavity Vertical-Cavity Surface Emitting Lasers

Currently VCSEL (Vertical Cavity Surface Emitting Laser) is one of the most active research problems in the field of optoelectronics. It has more advantages than EEL (Edge Emitting Laser) such as very lower threshold current, smaller far-field divergent angle, circular beams compatible with optical fibers, and easy to realize single longitudinal mode operation and 2-dimension integration etc. So it is widely used in the fields such as fiber communication, light-information processing, lasers print and light-sensor and so on. CC-VCSEL (Coupled-Cavity Vertical-Cavity Surface-Emitting Laser) inherited all the advantage of VCSEL, and it can achieve dual-wavelength output and wavelength conversion. So it will play important roles in DWDM, THz frequency generator and dual-wavelength measure.CC-VCSEL can operate on either of the two wavelengths supported by the structure, or on both wavelengths simultaneously, and the spectral interval between the two longitudinal modes depends on the number of periods in middle DBR and the detuning of the top cavity and bottom cavity. In this paper, we first establish the transfer matrix model about the entire CC-VCSEL embarks from the CC-VCSEL internal structure. Then the emission wavelength is calculated by transfer matrix method under the fixed carrier density. At last the effect of the number of periods in middle DBR, the detuning of the top cavity and bottom cavity, and the quantum well carrier density to the emission wavelength is analyzed. The result indicated that the spectral interval between the two longitudinal modes varying from 0.6nm to 58nm with the center of 940nm when the top cavity and the bottom cavity is symmetry.CC-VCSEL with two injection currents pumping can operate on two wavelengths models, may operate on four kinds of condition, so its threshold current is complex. In the second part of this paper the condition when CC-VCSEL achieved threshold is confirmed by analyzing the reflect gain at first. Then the threshold carrier density is calculated by transfer matrix method and threshold current curve is calculated by carrier rate equation under steady-state conditions. At last the relation between the threshold current and the state of emission is discussed.