NDLI: Direct observation of slow light in the noise spectrum of a laser

Content Provider	IEEE Xplore Digital Library
Author	El Amili, A. Miranda, B.-X. Goldfarb, F. Baili, G. Beaudoin, G. Sagnes, I. Bretenaker, F. Alouini, M.
Copyright Year	2011
Description	Author affiliation: Laboratoire de Photonique et Nanostructures, CNRS, Route de Nozay, 91460 Marcoussis, France (Beaudoin, G.; Sagnes, I.) \|\| Institut de Physique de Rennes, CNRS-Universit de Rennes I, 35042 Cedex, France (Alouini, M.) \|\| Laboratoire Aimé Cotton, CNRS-Université Paris Sud 11, 91405 Orsay Cedex, France (El Amili, A.; Miranda, B.-X.; Goldfarb, F.; Bretenaker, F.) \|\| Thales Research and Technology, Campus Polytechnique, 91127 Palaiseau Cedex, France (Baili, G.)
Abstract	Coherent population oscillations (CPO), an ubiquitous mechanism inducing slow and fast light (SFL), is present in any active medium provided that a strong optical beam saturates this medium. Thus, CPO must be present in any single frequency laser since the oscillating beam acts as a strong pump which saturates the active medium. This effect could be observed using an external probe whose angular frequency is detuned with respect to the oscillating mode, by less than the inverse of the population inversion lifetime. This effect should be visible in the laser excess noise, using the spontaneous emission present in the non-lasing side longitudinal modes of a single-frequency laser as probe of the CPO effect. Class-A vertical external cavity surface emitting semiconductor lasers (VECSELs) [1] recently developed for their low noise characteristics make them perfectly suited for the observation of CPO induced SFL in their noise spectrum. The single-frequency laser used in our experiment is a VECSEL which operates at ∼ 1 µm. We focus on the excess noise due to the beat notes between the laser line and the spontaneous emission noise at neighboring longitudinal mode frequencies [2,3]. At the $p^{th}$ FSR frequency pΔ, the noise spectrum is thus the sum of two Lorentzian peaks due to the beat notes of the lasing mode with the corresponding sidebands $(p^{th}$ and $−p^{th}$ modes). When the pumping rate is increased, we found experimentally that the excess noise consists of two peaks separated by δf = fp − f−p ∼ 100 kHz (inset of Fig.1(a)). This frequency shift is given by: δf ≈ ν0Lm over L+n0Lm(δnp+δn−p), where n0 is the bulk refractive index of the semiconductor structure, L and Lm are the length of the cavity and the gain medium respectively. δn±p are the modifications of the refractive index of the structure experienced by the ±p side modes and induced by the dispersion associated with the CPO effect. In a semiconductor active medium, thanks to the Bogatov effect [4], the dispersion is not an odd function of the frequency detuning with respect to ½0. Thus, δnp ≠ −δn−p and the two beat note frequencies fp and f−p corresponding to the p and −p modes occur at slightly different frequencies, as evidenced by the double peak of Fig.1(a). This CPO induced index modification can be derived from the gain medium rate equation including the phase-intensity coupling coefficient α (Henry's factor) that is responsible for the Bogatov effect. This CPO effect is also responsible for the modification of the refractive index seen by the side modes which modifies the round-trip phase accumulated by each side mode Fig.1(b). Notice also that since the cavity FSR Δ is sufficiently large that we are probe the wings of the dispersion profile of Fig.1(b), i. e., in the slow light regime. In conclusion, we experimentally evidenced the existence of intracavity slow light effects in a laser induced by the CPO mechanism. These effects are probed by the laser spontaneous emission noise present in the non lasing modes.
Starting Page	1
Ending Page	1
File Size	174179
Page Count	1
File Format	PDF
ISBN	9781457705335
e-ISBN	9781457705328
DOI	10.1109/CLEOE.2011.5942591
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2011-05-22
Publisher Place	Germany
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Content Type	Text
Resource Type	Article

Sl.	Authority	Responsibilities	Communication Details
1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
5	Website/Portal (Helpdesk)	Queries regarding NDLI and its services	support@ndl.gov.in
6	Contents and Copyright Issues	Queries related to content curation and copyright issues	content@ndl.gov.in
7	National Digital Library of India Club (NDLI Club)	Queries related to NDLI Club formation, support, user awareness program, seminar/symposium, collaboration, social media, promotion, and outreach	clubsupport@ndl.gov.in
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