Design of the active region and analysis of temperature sensitivity of high-temperature operating 795-nm special
VCSELs for Chip-Scale Atomic Clock (CSAC) are presented. Composition and thickness of the InAlGaAs multiple
quantum wells (MQWs) are optimized at room and elevated temperatures. Temperature sensitivity of the threshold
current is analyzed by calculating the temperature dependence of cavity-mode gain over a broad temperature range
(25°C-150°C). A self-consistent VCSEL model based on quasi 3D finite element analysis is employed to investigate selfheating
effects and temperature distribution in the proposed structure. Output power of 2.5mW is expected from 10μm
aperture VCSELs at 10mA current at ambient temperature of 358K.
Power scaling and beam divergence compression of 980 nm bottom-emitting vertical-cavity surface-emitting lasers
(VCSELs) are presented in this paper. First, the relationships among the reflectivity of the n-doped distributed Bragg
reflector, threshold current, and output power were analyzed, and the n-DBR reflectivity was optimized to achieve higher
slope efficiency in a relatively low threshold current. Second, the influence of the p-contact on the current density
distribution inside the active region was analyzed using the three-dimensional finite-element method. Uniform current
distribution was achieved by optimizing the diameter of the p-contact, and a consequent improvement in beam
divergence was observed. A low divergence of 5.4° was obtained for a single device with continuous-wave (CW) of 1.46
W at room temperature. The 8×8 VCSEL array showed a divergence angle of 10.2° at 4A. This array afforded a CW
output power of 1.95 W under an injected current of 4 A and a pulse output power of 115 W under a pulse drive current
of 130 A, a pulse width of 100 ns, and a repetition frequency of 100 Hz. VCSEL array chips were packaged in series to
form a “quasi-array” to further increase the output power. This series achieved a peak output power of 475 W under a
pulse drive current of 120 A.
A novel 980nm bottom-emitting VCSELs array with high power density and good beam property of Gaussian far-field
distribution is reported. This array is composed of 5 symmetrically-arranged elements of 200&μm,150μm and
100μm-diameterμwith the center spacings of 300μm and 250μm respectively. The maximum power is 880mW at a
current of 4A, corresponding to 1KW/cm<sup>2</sup> average optical power density. The differential resistance is Ω with a
threshold of 0.56A. The novel array is compared with a 300μm-aperture-size single device and a 4*4 2-D array with
50μm element aperture size and 250μm centre spacing. The three devices have the same lasing area. The conclusion is
that the novel array is better in the property of output power, threshold current, lasing spectra, far-field distribution etc.
Whispering-Gallery-Mode (WGM) photonic crystal microcavity is a kind of photonic crystal application and can
potentially be used for miniaturized photonic devices, such as thresholdless lasers. In this paper we study the WGM of
photonic crystal microcavities focusing on the so called H2 cavities which are formed by removing seven air holes. The
WGM in these large-size cavities has some advantages compared with single defect WGM in the view of real device
applications. We further add a central air hole in the cavity region to analyze the effect on WGM in the microcavity by
finite difference time domain (FDTD) and plane wave expansion (PWE). It is found that the tolerance of WGM is large
enough for the fabrication of electrical injection structure.