Quantum noise and polarization properties of vertical-cavity surface-emitting lasers

Abstract

We present theoretical and experimental results on the quantum noise performances of vertical-cavitysurface-emitting-lasers ͑VCSELs͒. Using a semiclassical laser noise approach, we demonstrate that the ratio M ϭS / P of the powers in the two polarization modes of the laser is one of the essential parameters governing the VCSELs quantum noise behavior. The generation of amplitude squeezed states of light is only possible for two well-selected cases which are the ideal two-polarization-mode laser (M Ϸ1) and the ideal singlepolarization-mode laser (M Ϸ0), respectively. Furthermore, we show that gain suppression, as well as other relevant semiconductor parameters, have also to be taken into account to model realistically the VCSEL's quantum noise. These theoretical investigations are very well supported by our experimental results. We demonstrate experimentally that indeed there exists a direct link between the parameter M and the shot noise normalized amplitude noise. In a two-polarization-mode laser as, e.g., represented by a large diameter air-post VCSEL, squeezed states could not be generated because of insufficiently low values of M even though a strong anticorrelation between the two modes exists. With a single-polarization-mode laser, as realized with small diameter oxide confined VCSELs, we have been able to demonstrate the generation of single-mode squeezed light with a VCSEL. A squeezing level of 0.9 dB has been measured, which with the detection efficiency corrected, results in 1.3 dB at the VCSEL upper facet. ͓S1050-2947͑99͒08010-5͔

Understanding VCSEL-Based Gain Switching Optical Frequency Combs: Experimental Study of Polarization Dynamics

“…Besides, the noise floor in the P-OFCG curve is close to the reference one and then the total comb is a signal with high coherence between all its modes as we were expecting taking into account our previous results [7]. This high coherence is driven by the GS regime because the polarization modes of a VCSEL are in CW operation anti-correlated regarding [10], [11].…”

“…On the other hand, and more importantly, we have seen how these orthogonally polarized combs that appear are related in phase and collaborate to produce a wider overall total comb. This is remarkable if we take into account that the two modes present high anticorrelation if no modulation is applied as it is stated in [10], [11]. Therefore, this will imply that the phase correlation is caused by the GS regime.…”

Quantum noise and spatial emission properties of RCLEDs

“…28,29 The fact that the highest amount of squeezing is not observed at the highest pumping current can be explained by heating of the device at the highest pumping current and the accompanied deterioration of the quantum efficiency, an effect which has also been observed experimentally for VCSELs and modeled accordingly theoretically. 11 Another reason might be the influence of the in RCLEDS already present resonator, resulting in the specific spectral and angular dependence of the emission of RCLEDs. These resonator characteristics can introduce additional noise similar to multimode competition in semiconductor lasers when detecting with spectral or spatial selectivity.…”

“…The possibility of generating non-classical states of light with sub-shot noise fluctuations (amplitude squeezing) with semiconductor optoelectronic emitters was demonstrated theoretically 3 and experimentally. 4 Since then extensive work with the aim to understand and to improve the squeezing performances of semiconductor lasers [5][6][7][8][9] including vertical-cavity surface-emitting lasers (VCSELs) [10][11][12][13][14][15] has been performed. However, the real world of lasers showed up to be more or less far away from the ideal candidate leading to the fact that 8.3 dB of squeezing 5 still represents the record and that typically between 1 and 3 dB are obtained with experiments in the last years.…”

Effect of field and medium asymmetries on enhancement of signal-to-noise ratio

“…It has been reported that nonlinear anisotropy is the root cause of polarization switches in vertical cavity surface emitting lasers (VCSELs). A sudden change in the polarisation state of light coming from VCSEL occurs with change in the laser current (Vey et al 1999). It has been predicted that the polarization fluctuations in the emitted light, driven by spontaneous emission noise and modified by optical anisotropies can become exceptionally strong in case of VCSELs.…”