Alexandre Bacou

Long Wavelength VCSEL-by-VCSEL Optical Injection Locking

Vertical-cavity surface-emitting laser (VCSEL)-by-VCSEL optical injection locking to obtain high cutoff frequencies of 1.3-mum VCSELs is demonstrated. A detailed physical explanation of the underlying mechanism is presented. VCSELs from the same wafer have been used in a master-follower configuration. Two probe stations are used in this experiment to power-up two VCSELs simultaneously. Polarization insensibility of the injection locking is demonstrated and a novel architecture is proposed to achieve cutoff frequency doubling. For the first time, a high cutoff frequency is achieved through optically injection locking the satellite mode of a long wavelength VCSEL. Injection-locking spectra with variable injection powers and variable detuning values have been obtained and methods have been proposed to obtain high cutoff and/or resonance frequencies. A rate-equation-based model is presented. Simulations have been carried out using this model. Finally, a linear increases in the follower VCSEL cutoff frequency with increasing injected power is demonstrated by using a semiconductor optical amplifier.

Electrical Modeling of Long-Wavelength VCSELs for Intrinsic Parameters Extraction

We present an efficient method to model the small- signal modulation response of a long-wavelength VCSEL chip using an equivalent electrical circuit. This circuit serves two distinct purposes. Based on T-matrix formalism, it is used to remove the parasitics contribution originating from the electrical access of the chip in order to obtain the optical cavity intrinsic frequency response as defined by the rate equations. The same circuit is also used to extract the intrinsic cavity parameters since every circuit element represents a physical optical cavity entity. The extraction of reliable intrinsic parameters requires that the circuit element values be representative of the device under test. To achieve this, we have developed a new methodology based on static and dynamic measurements such as the S-parameters and the turn-on delay time. In accordance with this procedure, each element of the cavity is fixed without numerical optimization. The good agreement between measured and simulated curves confirm the validity of the technique used.

VCSEL Intrinsic Response Extraction Using

We present a new method to remove the parasitics contribution to the vertical-cavity surface-emitting laser (VCSEL) chip response, in order to obtain the intrinsic S 21 behavior. We demonstrate that the chip can be split into two cascaded subsystems representing the electrical access and the optical cavity, respectively. An equivalent electrical circuit defining the behavior of the electrical access is combined with T -matrix formalism to remove the parasitics contribution from the measured S 21 response. Results allow us to determine the intrinsic 3-dB bandwidth of the VCSEL.

T

For a long time, only a small wavelength range of Vertical-Cavity Surface-Emitting Lasers (VCSEL) was available. The current evolution in process technology allows the fabrication of long wavelength VCSEL that is interesting for Telecom systems because they offer a higher integration level than the existing optical sources at lower costs since they are fabricated in arrays. We propose to focus our investigation on the behavior of singlemode 1.55μm VCSEL. We aim at precisely knowing their spectral properties under direct modulation. We present a study about the linewidth measurement and the linewidth enhancement factor, also called the Henry - or the alpha - factor. Many studies have been reported but only a few of them are really efficient. Two different set-ups are presented here to extract alpha factor. The first one uses an interferometer based on the heterodyne technique and the second uses the dispersive properties of an optical fiber. We compare both results and discuss about each set-up.

-Matrix Formalism

Since the telecommunication revolution in the early 90s, that saw massive deployment of optical fibre for high bit rate communications, coherent optical sources have made tremendous technological advances. The technological improvement has been multi dimensional; component sizes have been reduced, conversion efficiencies increased, power consumptions decreased and integrability into compact optoelectronic sub-modules improved. Semiconductor lasers, emitting in the 1.1-1.6 μm range, have been the most prominent beneficiaries of these technological advances. This progress is a result of research efforts that consistently came up with innovative solutions and components, to meet the market demand. This in-phase, demand and supply, problem and solution and consumer need and innovation cycle, has ushered us in to the present information technology era, where stable high speed data links make the backbone of almost every aspect of life, from economy to entertainment and from health sector to defence production. By the start of twenty-first century, a new, low cost, low power consumption and miniaturized generation of lasers had started to capture its own market share. These lasers, named Vertical-Cavity Surface-Emitting Lasers (VCSELs) due to the presence of an optical cavity which is normal to the fabrication plane , have established themselves as premier optical sources in short-haul communications such as Gigabit Ethernet, in optical computing architectures and in optical sensors. While shorter wavelength VCSEL (< 1μm) fabrication technology was readily mastered, due to the ease in manipulation of AlGaAs-based materials, long wavelength VCSELs especially VCSELs emitting in the 1.3-1.5 μ range have encountered several technical challenges. There importance as low-cost coherent optical sources for the telecommunication systems is primordial, since they are compatible with the existing infrastructure. VCSEL utilization in low-cost systems imply the application of direct modulation for high bit rate data transmission which engenders the problems of frequency chirping which increases laser linewidth and severely limits the system performance. Furthermore, relatively lower VCSEL intrinsic cut-off frequencies translated in to impossibility of achieving high bit rates. Optical injection-locking is proposed as a solution to these problems. It enhances the intrinsic component bandwidth and reduces frequency chirp considerably. Source: Advances in Optical and Photonic Devices, Book edited by: Ki Young Kim, ISBN 978-953-7619-76-3, pp. 352, January 2010, INTECH, Croatia, downloaded from SCIYO.COM

Spectral behavior of long wavelength VCSELs

We present here a 1.55 mum single mode vertical-cavity surface-emitting laser (VCSEL) based low phase-noise ring optoelectronic (OEO) oscillator operating at 2.49 GHz for aerospace, avionics and embedded systems applications. Experiments using optical fibers of different lengths have been carried out to obtain optimal results. A phase-noise measurement of -107 dBc/Hz at an offset of 10 kHz from the carrier is obtained. A 3-dB linewidth of 16 Hz for this oscillator signal has been measured. An analysis of lateral mode spacing or free spectral range (FSR) as a function of fiber length has been carried out. A parametric comparison with DFB laser-based and multimode VCSEL-based opto-electronic oscillators is also presented.

Optical Injection-Locking of VCSELs

Microwave performance of 1.3 mum optically injection-locked single-mode VCSELs functioning at room temperature is presented. The experiment has been performed using two identical unpackaged VCSELs on two separate probe-stations. Three-fold increase in the 3-dB cut-off frequency of S21 spectra have been observed under VCSEL-by-VCSEL optical injection-locking.