VCSEL Fundamentals

Abstract

In this chapter we outline major principles of vertical-cavity surfaceemitting laser (VCSEL) design and operation. Basic device properties and generally applicable cavity design rules are introduced. Characteristic parameters like threshold gain and current, differential quantum efficiency and power conversion efficiency, as well as thermal resistance are discussed. We describe the design of Bragg reflectors and explain the transfer matrix method as a convenient tool to compute VCSEL resonator properties in a one-dimensional approximation. Experimental results illustrate the emission characteristics of high-efficiency VCSELs that apply selective oxidation for current and photon confinement. Both the 850 and 980 nm wavelength regions are considered. The basic treatment of laser dynamics and noise behavior is presented in terms of the small-signal modulation response as well as the relative intensity noise. Finally we give some examples of VCSEL applications in fiber-based optical interconnects, i.e., optical data transmission over short distances. IntroductionVCSELs have undergone an extraordinary evolution over the past three decades. Suggested by Prof. Kenichi Iga and first demonstrated by the research group at Tokyo Institute of Technology in the late 1970s [1-3], VCSELs are a commodity item today [4] and already serve millions of computer users as the key component in modern navigation devices such as the optical mouse. In even larger quantity, this laser type has entirely replaced edge-emitting laser diodes for use in multimode fiber-based Gbit/s speed optical data transmission in premises networks and for the interconnection of various kinds of computer clusters. Several books entirely devoted R. Michalzik (B)

Energy efficiency, bit rate, and modal properties of 980 nm VCSELs for very-short-reach optical interconnects

“…The resulting thermal resistance (R thermal = ΔT/ΔP diss ) of our 980 nm VCSEL is ~2.8 K/mW. This value is about what would be expected (possibly slightly higher) for an oxide VCSEL with an oxide aperture diameter of ~7.0 μm [8]. We note that we may reduce the thermal resistance by replacing some or all of our high index AlGaAs DBR layers with GaAs high index DBR layers.…”

“…GaAs-based infrared VCSEL with DBRs composed of AlGaAs [8]. The resulting thermal resistance (R thermal = ΔT/ΔP diss ) of our 980 nm VCSEL is ~2.8 K/mW.…”

Silicon-Integrated Hybrid-Cavity 850-nm VCSELs by Adhesive Bonding: Impact of Bonding Interface Thickness on Laser Performance

“…Minimum threshold current (1.1 mA) is obtained for HC-VCSEL B which has the smallest gain-to-resonance detuning at 25°C. At higher ambient temperatures, HC-VCSELs C and D have lower threshold currents since the detuning is reduced with temperature as a result of the ∼4 times faster redshift of the gain peak with respect to the cavity resonance [15]. The threshold currents from Fig.…”

Numerical model for small-signal modulation response in vertical-cavity surface-emitting lasers

“…Despite the development in the technology, the existing models for the modulation performance of VCSELs and semiconductor lasers in general are still ineffective. The existing models of modulation response are based on many parameters whose values can be chosen arbitrarily to a certain extent, or have to be fitted to experiment [10][11][12][13][14][15][16]. These models have shown that the approach based on rate equations can give good agreement with the small-signal modulation (SSM) response experiment.…”