Suchergebnisse

3 pages, 3 figures.-- Printed version published Jul 1, 2009. ; We introduce a new technique for the measurement of inertial rotations using a semiconductor ring laser. Inertial rotation introduces a frequency deviation of the optical frequency of the two counterpropagating waves in the laser cavity, whereas mode coupling causes frequency attraction (frequency pushing) and finally locking at low rotation rates, washing out the small Sagnac frequency difference to be measured. Here we propose to measure inertial rotation whitin the so-called locking band using the phase/amplitude dependence on detuning found for the oscillating modes under the gain line. The dephasing accumulated by the two counterpropagating waves unbalances the fields' amplitudes within the locking region. We analytically derive the responsivity function quantifying the two-mode power unbalance versus rotation rate, by means of a two-mode rate equations model. Noise performance of a possible rotations sensor are also discussed by calculating the noise equivalent rotation rate. ; This work was supported by the European Union project IOLOS-FP6-IST-2005-34743, by the Spanish Government project PhoDeCC TEC2006-10009/MIC, and by the Balear Government project QULMI PROGECIB-5A. The work of A. Scirè was supported by the Ramón y Cajal program by Spanish MEC. ; Peer reviewed

En: Conference semiconductor lasers and laser dynamics III, Strasbourg (France), 7 April 2008. Eds. Krassimir P. Panajotov, Marc Sciamanna, Angel A. Valle, Rainer Michalzik.-- Published Online: 5 May 2008.-- 8 pages, 3 figures. ; We analyze a rate equation model in the Langevin formulation for the two modes of the electric field and the carrier density, modelling the spontaneous emission noise in a semiconductor ring laser biased in the bidirectional regime. We analytically investigate the influence of complex backscattering coefficient when the two modes are reinterpreted in terms of mode-intensity sum (I-Spectrum) and difference (D-spectrum). The D-spectrum represents the energy exchange between the two counterpropagating modes and it is shaped by the noisy precursor of a Hopf bifurcation influenced mainly by the conservative backscattering. The I-Spectrum reflects the energy exchange between the total field and the medium and behaves similarly to the standard relative intensity noise for single-mode semiconductor lasers. Good agreement between analytical approximation and numerical results is found. ; This work was funded by the european project IOLOS IST-2005-34743 and Balear Government project QULMI PROGECIB-5A. A.S. and R.Z. acknowledge Ram´on y Cajal program by Spanish MEC. ; Peer reviewed

3 pages, 7 figures.-- PACS: 42.55.Px, 42.60.By ; We have experimentally and theoretically analyzed the modal properties of semiconductor ring lasers and the wavelength jumps that occur in connection with directional switching above the threshold. ; We acknowledge financial support from the IOLOS 034743 project funded by the European Union's Sixth Framework Program (EU FP6-2005-IST-5), the PhoDeCC (TEC2006-10009/MIC) project funded by the Spanish Ministerio de Educación y Ciencia MIC , the QULMI (PROGECIB-5A) project funded by the Spanish Govern Balear, and the TEC2006-13887-C05-03 project funded by the Spanish Ministerio de Educación y Ciencia. ; Peer reviewed

ISLC 2008. IEEE 21st International 14-18 Sept. 2008 ; We have experimentally and theoretically analyzed the modal properties of semiconductor ring lasers and the wavelength jumps that occur in connection with directional switching above threshold ; This work was funded by the European project IOLOS IST- 2005-34743, Spanish project PhoDeCC TEC2006-10009/MIC and Balear Government project QULMI PROGECIB-5A. A.S. acknowledges Ram´on y Cajal program by Spanish MEC. S.B. and J.J. acknowledge financial support from project TEC2006- 13887-C05-03. J.J. acknowledges support from the Juan de La Cierva program by the Spanish MEC. ; Peer reviewed

We have analyzed experimentally and theoretically the modal properties of a semiconductor ring laser and the wavelength jumps that occur in connection with directional switching above threshold. A transfer matrix analysis allow us to explain the transfer function measurements when amplified spontaneous emission in the cavity is accounted for. Moreover the transfer matrix analysis permits to determine the threshold condition for the laser modes, which split in two branches due to the symmetry breaking imposed by the output coupler and output waveguides. The wavelength jumps displayed by the device above threshold are interpreted with the frequency splitting and threshold difference between these two branches of solutions, together with the redshift of the material gain. ; We acknowledge financial support from project IOLOS, FP6-2005-IST-5. S. B. acknowledges financial support from project TEC2006-13887-C05-03. A.P. and A.S. acknowledge Balear Government project QULMI PROGECIB-5A. A.S. acknowledges Ram´on y Cajal program by Spanish MEC ; Peer reviewed

OCIS codes: (140.3560) Lasers, ring; (140.5960) Semiconductor lasers; (200.4660) Optical logic.-- Final full-text version of the paper available at: http://dx.doi.org/10.1364/OE.15.012941. ; Semiconductor ring lasers display a variety of dynamical regimes originating from the nonlinear competition between the clockwise and counter-clockwise propagating modes. In particular, for large pumping the system has a bistable regime in which two stationary quasiunidirectional counter-propagating modes coexist. Bistability is induced by cross-gain saturation of the two counter-propagating modes being stronger than the self-saturation and can be used for data storage when the semiconductor ring laser is addressed with an optical pulse. In this work we study the response time when an optical pulse is injected in order to make the system switch from one mode to the counter-propagating one. We also determine the optimal pulse energy to induce switching. ; This work has been funded by the Spanish MEC and Feder under project TEC2006-10009/MIC (Conoce 2) and FIS2004-00953 (PhoDeCC), by the European Community under projects IST-2005-34743 (IOLOS) and IST-2005-34551 (PICASSO), and by the Balear Government under project PROGECIB-5A (QULMI). T.P. acknowledges support from the Govern Balear (Spain). A.S. acknowledges Ramón y Cajal program by MEC. G.V. is a Postdoctoral Fellow of the Research Foundation - Flanders (FWO).

9 pages, 7 figures. ; Theory and experiments of single-mode ridge waveguide GaAs-AlGaAs semiconductor ring lasers are presented. The lasers are found to operate bidirectionally up to twice the threshold, where unidirectional operation starts. Bidirectional operation reveals that just above threshold, the lasers operate in a regime where the two counterpropagating modes are continuous wave. As the injected current is increased, a new regime appears where the intensities of the two counterpropagating modes undergo alternate sinusoidal oscillations with frequency in the tens of megahertz range. The regime with alternate oscillations was previously observed in ring lasers of the gas and dye type, and it is here reported and investigated in semiconductor ring lasers. A theoretical model based on a mean field approach for the two counterpropagating modes is proposed to study the semiconductor ring laser dynamics. Numerical results are in agreement with the regime sequence experimentally observed when the injected current is increased (i.e., bidirectional continuous-wave, bidirectional with alternate oscillations, unidirectional). The boundaries of the different regimes are studied as a function of the relevant parameters, which turn out to be the pump current and the conservative and dissipative scattering coefficients, responsible for an explicit linear coupling between the two counterpropagating field modes. By a fitting procedure, we obtain good numerical agreement between experiment and theory, and also an estimation for the otherwise unknown scattering parameters. ; The work of M. Sorel and A. Scirè was supported by the European Union under Marie Curie Fellowship Contracts HPMF-CT-1999-00083 and HPMF-CT-2000-00617. ; Peer reviewed

3 pages, 3 figures.-- OCIS codes: 140.3560, 230.3120, 190.3100. ; Full-text version available Open Access at: http://www.ifisc.uib.es/publications/downfile.php?fid=3578 ; We report on fabrication and characterization of single-longitudinal- and transverse-mode semiconductor ring lasers. A bifurcation from bidirectional stable operation to a regime with alternate oscillations of the counterpropagating modes was observed experimentally and is theoretically explained through a two-mode model. Analytical expressions for the onset and the frequency of the oscillations are derived, and L–I curves numerically evaluated. Good quantitative agreement between theory and measurements made over a large number of tested devices is obtained. ; A. Scirè thanks the European Union for the financial support of a Marie Curie fellowship under contract HPMF-CT-2000-00617. ; Peer reviewed

4 pages, 2 figures.-- PACS nrs.: 42.65.-k; 42.55.Px; 42.60.Mi. ; We investigate both theoretically and experimentally the stochastic switching between two counterpropagating lasing modes of a semiconductor ring laser. Experimentally, the residence time distribution cannot be described by a simple one-parameter Arrhenius exponential law and reveals the presence of two different mode-hop scenarios with distinct time scales. In order to elucidate the origin of these two time scales, we propose a topological approach based on a two-dimensional dynamical system. ; This work has been partially funded by the European Union under project IST-2005-34743 (IOLOS). This work was supported by the Belgian Science Policy Office under grant No. IAP-VI10. G.V. is a Postdoctoral Fellow and LG is a PhD Fellow of the Research Foundation - Flanders (FWO). ; Peer reviewed