Small-signal properties of 650-nm vertical-cavity surface-emitting lasers (VCSELs) with different oxide aperture sizes were measured. A small diameter VCSEL of 3.5 mum has a maximum resonance frequency of 5.7 GHz. The photon density determines the maximum resonance frequency. Modeling also indicates higher photon densities in the small VCSEL due to better thermal behavior

In this paper we discuss the problems of the AlGaInP material system and its consequences for the laser applications in vertical-cavity surface-emitting lasers (VCSEL). The epitaxial and technological solutions to overcome at least parts of the inherent problems were presented. Measured power-current curves of 660nm AlGaInP-based oxide-confined VCSEL are compared with calculated data by a cylindrical heat dissipation model to improve heat removal out of the device. Pulsed lasing operation of a 670nm VCSEL at +120 degrees C heat sink temperature is demonstrated, where we exceeded 0.5mW and at +160 degrees C still 25 mu W output power were achieved. NW also studied the modulation bandwidth of our devices and achieved 4GHz and calculations lead to a maximum possible intrinsic -3dB frequency of 25GHz.

This talk focuses on the high frequency characteristics of red VCSELs. After a short description of important fabrication issues the modulation behaviour of GaInP surface emitting lasers is discussed on the basis of the laser rate equations. The influence of the geometric dimensions of the laser structure and of the operating conditions is investigated. From the S-parameter analysis a modulation coefficient of 3 GHz/(mA)(1/2) for VCSELs with a 7 gm aperture and a differential gain of 1.15 (.) 10(-16) cm(2) are deduced. A more detailed analysis reveals, that the modulation behaviour of red VCSELs nearly solely depends on their photon density inside the quantum wells as expected from the rate equations. These results imply that for a certain range of geometries diffusion and diffraction have a second order influence on the high frequency characteristics of red VCSELs. The K-factor analysis indicates very short carrier transfer and relaxation times around 5 ps and a maximum frequency of 25 GHz. Large signal modulation issues such as the properties of the eye diagram are also addressed. From the device characteristics it is concluded that the GaInP-VCSEL is suitable for data communication applications. Low cost fabrication makes the red VCSEL an attractive candidate for both automotive and high-speed data communication.

Measured power–current curves of 660 nm AlGaInP-based oxide-confined vertical-cavity surface-emitting lasers (VCSEL) are compared with calculated data by a cylindrical heat dissipation model to improve heat removal out of the device. Pulsed lasing operation of a 670 nm VCSEL at high temperatures is demonstrated. At +120 °C heat sink temperature we exceeded 0.5 mW and at +160 °C still 25μW output power were achieved.

Pulsed lasing operation of a 670 mn AlGaInP-based oxide-confined vertical-cavity surface-emitting laser (VCSEL) at high temperatures is demonstrated. At +120degreesC heatsink temperature output power exceeded 0.5 mW and at +160degreesC 25 muW output power was achieved.

We experimentally investigate the transverse mode and polarisation behaviour of multimode red VCSELs in the GaInP/AlGaInP material system, emitting at 670nm. These devices were fabricated at the University of Stuttgart. More in particular we have measured the optical efficiencies, divergence and far field characteristics of the laser beams, thermal resistivities, polarization behaviour and optical spectra of the emitted radiation on two different dies. Despite multimode emission from threshold onwards, the output beam of these VCSELs is much less divergent than their 850nm counterparts. Moreover, these red VCSELs feature smaller thermal resistivities but suffer from early thermal roll-off. To conclude we present results on the polarisation behaviour of the VCSELs.

Vertical cavity surface emitting lasers (VCSEL) in the GaInP/AlGaInP material system have experienced a rapid development in their short history. In general lasers from that material system are suitable for a huge number of applications beginning with TV lasers and high power lasers for edge emitters, continuing with optical data storage, medical applications as well as data communication in cars, air planes, offices and between computers as application field for VCSELs. Especially automotive applications show the highest requirements on a laser with respect to operation temperature and power. In this talk we draw out the problems of the material system AlGaInP and its implications for laser applications. We discuss the epitaxial and technological solutions to overcome at least a part of these inherent problems. We will discuss the possible power that we can expect from VCSELs emitting in the range between 650 nm to 670 nm. We got from our lasers 5 mW, CW RT, 670nm and 2.5mW, CW@RT, 650 nm. We emphasize the role of doping, Bragg mirror grading, suitable detuning of cavity mode and gain, and optimisation of the contact layer and control of the oxide aperture in the VCSEL structure to get improved operation characteristics at higher temperatures. From the analysis of high frequency measurements, we could evaluate modulation bandwidths between 4 GHz and 10 GHz. The application of polyimide as a dielectric isolation material shows the potential to obtain modulation bandwidths beyond 10 GHz. For the intrinsic modulation bandwidth we get a value of 25 GHz, which is near the value edge emitters show. A more detailed discussion on photon lifetimes and carrier transport times will be given in the talk. Red light emitting VCSELS driven with short current pulses showed laser emission up to + 160 degreesC case temperature. Thus, a CW operation up to +120 degreesC can be expected after further improvement of power generation (decrease of series resistance) and heat spreading (optimised contacts and mounting). From these characteristics we can conclude that AlGaInP-surface emitting lasers have a real potential as low cost lasers for automotive applications as well as data communication applications up to 10 GHz.

Summary form only given. Since the first realisation of visible red VCSELs by R.P. Schneider et al. (1993), these devices are attracting more and more interest by science and industry because of their promising application in plastic fiber communication systems. In this paper, we present our approach to realize red VCSELs. We use AlAs/Al/sub 0.5/Ga/sub 0.5/As for the Bragg mirrors and (Al/sub 66/Ga/sub 34/)/sub 5/In/sub 5/P/(Al/sub 33/Ga(67))/sub 5/In/sub 5/P/Ga/sub 40.4/In/sub 59./ /sub 6/P for the active region (quantum well thickness is 6 nm). We use 55/36 mirror pairs for the n/p-side. We also made investigations to reduce the number of mirror pairs. Our devices have a 3/2/spl lambda/-cavity with a node of the electric field at the interface of the optical cavity and the mirror (this is to reduce possible absorption at the P/As interface). We match the optical cavity with the Bragg mirror reflectance, as well as the emission wavelength of the quantum well. We also investigated the effect of gain detuning with respect to the cavity.

In this work, we have investigated the design and metalorganic vapor-phase epitaxial growth of red vertical cavity surface-emitting lasers (VCSEL, emission wavelength around 650–680 nm) with respect to low threshold current densities and a reduced temperature dependence. A VCSEL in the red regime implies a combination of AlGaInP (cavity) and AlGaAs/AlAs (distributed Bragg reflectors). In order to check the influence of the epitaxially critical P/As-interface on the laser performance, we have grown edge-emitting lasers where we varied the distance between this interface and the active quantum wells. We observed no increase of the threshold currents even for small distances as necessary in VCSEL structures when applying an optimized switching sequence at these interfaces. Consequently, red VCSELs could be grown which showed continuous wave operation at room temperature (670 nm, 0.15 mW at 20°C). In order to improve the temperature sensitivity of these VCSELs, we have studied a large number of devices with well-defined misalignment between gain and Bragg mirror reflectivity. For lasers where this misalignment resulted in somewhat worse room temperature properties (e.g. threshold current densities around 800 A/cm2), we found a clearly enhanced temperature stability.