R. Santos

Experimental modulation bandwidth beyond the relaxation oscillation frequency in a monolithic twin-ridge laterally coupled diode laser based on lateral mode locking

Monolithic twin-ridge laterally coupled diode lasers emitting at 1.3microm are presented that have a small-signal modulation bandwidth beyond the relaxation oscillation frequency of a single ridge. Spectra and spectrally resolved far fields are presented for three bias conditions: only one ridge lasing, both ridges lasing just above threshold, and both ridges lasing at biases well above threshold. In the first two cases the spectrum has single-peaked longitudinal modes, whereas the third cases shows splitting to in-phase and out-of-phase modes. The splitting frequency of the optical spectrum is measured to be 7.7 GHz. Small-signal modulation measurements reveal a strong resonance at 7.7 GHz, demonstrating an effect of lateral mode locking. As a result of this effect, the twin-ridge laser can be made to have a -3-dB bandwidth beyond that associated with its relaxation oscillation frequency.

Influence of the relative bias current injection in the coupling of twin stripe diode lasers

In this work a study of the dependence of the coupling in laterally coupled diode lasers (LCDL) with the relative bias conditions is presented. The study is made by the analysis of the spectrally resolved near and far field optical spectrum combined with the frequency responses of these devices at different bias conditions. By the analysis of these measurements it was observed that three different operation regions appear, and are identified by the spectral phase relation between the fields emitted by each laser stripe.

Experimental evidence of coupling effects in a twin-ridge laser

We present for the first time (to our knowledge) experimental data on the intrinsic relaxation oscillation frequency in a twin-ridge laser array. We present a detailed analysis of the frequency response of the device, both under single-ridge operation as well as in twin ridge. We demonstrate the strong influence that the injection current on one ridge has over the relaxation oscillation frequency of the other. Using previously defined dependencies for the twin ridge, we link the imaginary part of the coupling constant to the observed variations in the relaxation oscillation frequency, proposing a procedure to determine a parameter that so far has been used as a free adjustment value.

Experimental measurements of the ridge spacing influence on the frequency response and optical spectrum of laterally coupled laser diodes

The objective of this work is to analyse the dependence of the frequency response of Laterally Coupled Diode Lasers (LCDL) focusing on the separation between the laser ridges. A detailed study of the integrated optical spectra and frequency response is presented for LCDLs with 300 μm cavity length and separation between the ridges of 2, 4, 6, 8 and 10 μm. This study is of major importance as it defines the range of frequency locking for each ridge spacing and also its dependence on the bias conditions applied.

High bandwidth small signal modulation response of two laterally mode-locked diode lasers

In this letter, we present the study of the small signal modulation response of a monolithic twin ridge laterally coupled diode lasers. Such structures have been extensively theoretically studied for their promising characteristics as high-speed optical sources for optical communications, and in this work we demonstrate the increase of the small signal bandwidth beyond the relaxation oscillation frequency with the appearance of a second peak in the small signal response due to the laterally mode locking of these two emitters.

64-Mb/s data transmission beyond the relaxation oscillation frequency using monolithically integrated two laterally coupled diode lasers

In this letter, we demonstrate the possibility of using two monolithically integrated laterally coupled diode lasers for data transmission beyond the intrinsic relaxation oscillation frequency of semiconductor lasers. The resonance of the lateral modes of such structure provides a peak in the small signal modulation response of the device above the relaxation oscillation frequency of the intrinsic emitters that is studied in terms of relative intensity noise and phase noise to characterize this new, simple, and compact device. Optical transmission of a 64-Mb/s pseudorandom bit sequence signal using a microwave carrier over this resonance peak of the lateral modes above the relaxation oscillation is demonstrated for the first time to our knowledge.

Experimental Observation of Chaotic Dynamics in Two Coupled Diode Lasers Through Lateral Mode Locking

The nonlinear and chaotic phenomena in lateral coupled diode lasers have been widely studied theoretically. In this work an experimental analysis of the complex nonlinear and chaotic dynamic regimes experimentally observed in these devices and the mechanisms that produces it is made. This analysis is set by means of the RIN electrical spectrum and of the high resolution Fabry-Perot optical spectrum. A mapping of the nonlinear occurrences in these devices is obtained and a study of the relation between the relaxation oscillation frequency and the lateral locking frequency is achieved.

Experimental analysis of the locking and nonlinear regimes in lateral coupled diode lasers

The emission characteristics and the dynamics of laterally coupled diode lasers have been theoretically studied by many authors. However, little experimental work has been done on the locking and nonlinear dynamics of coupled lasers. An experimental characterization of the emission and dynamic characteristics is made by means of the spectrally resolved far field and of the relative intensity noise (RIN) spectrum. It was observed that by varying the bias conditions applied to the device it operates in: (1) locking (lasing both out-of-phase and in-phase lateral modes) or in (2) unlocking. Also it was found that, when the device is lateral locked, several nonlinear and chaotic operation regimes may occur and that the amplitude of the RIN spectrum is highly dependent on the locking conditions.

Experimental investigation of the coupling dependence on the lateral separation in twin stripe diode laser arrays

The coupling phenomena dependence with the lateral separation between the laser stripes in laterally coupled diode lasers is of major importance for the design of these devices as a solution to overcome the intrinsic bandwidth limitation of semiconductor lasers. In this work an experimental study of the coupling dependence with the separation between laser stripes is presented. For that purpose a comparison of the spectrally resolved near and far fields and of the frequency responses obtained with the laterally coupled diode lasers for devices with different separation between the ridges is made.

Experimental and theoretical study of the frequency response of laterally coupled diode lasers

We report on the combined theoretical and experimental observation of an increase of the small signal modulation response of a Laterally Coupled Diode Laser (LCDL) system beyond its relaxation oscillation frequency. The increase is achieved by means of lateral coupling. Theoretical approaches are presented to explain the experimental observations obtained with these LCDL devices. Our results shed light on the principle of diode laser coupling an open up new perspectives for LCDL for high-speed optical communications.