Towards temporal cavity solitons in semiconductor ring laser

Presenter Notes

Towards temporal cavity solitons in semiconductor ring laser

Francois Gustave, Stéphane Barland

Institut Non Linéaire de Nice

inln

Funding

Agence Nationale de la Recherche project (ANR-12-JS04-0002-01) MOLOSSE: "mode-locking and solitons in semiconductors": http://molosse.org

Presenter Notes

Contents

Motivation and approach

Experimental system

  • Ring laser
  • Physical parameters
  • Optical injection

Observations

  • Directionality
  • Delay/space: plane wave and modulational instabilities, localization

Conclusion

Presenter Notes

Phase-locked localized states in the transverse plane

Presenter Notes

A paradigmatic system, Lugiato-Lefever equation:

  • Optical cavity filled with nonlinear medium + coherent forcing
  • Instantaneous nonlinearity
  • Kerr type
  • Single longitudinal mode
  • Periodic transverse boundary conditions

More realistic, but still theoretical:

  • Optical cavity filled with nonlinear medium + coherent forcing
  • 2-level atomic medium (not so fast, not Kerr): Saturable gain or absorption, phase-amplitude coupling
  • Single longitudinal mode
  • Periodic transverse boundary conditions, very large grid

Presenter Notes

One thing that worked in the end:

VCSEL-type semiconductor laser (class-B) with optical injection

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Note: Optical injection breaks phase symmetry, phase locked localized structures

Key ingredients:

  • Very far apart longitudinal resonances
  • Weak gain guiding mechanism and large Fresnel number \(a^2/\lambda L\)
  • Optical gain (saturable nonlinearity) proved extremely useful

Presenter Notes

Phase-locked localized states along propagation

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Nonlinear optical fiber ring cavity with coherent forcing

  • Described with an LL-like model, except diffraction is replaced by a dispersion operator (Leo et al, Nat. Phot. (2010), see also W. Firth, Nat. Phot. (2010))
  • Single transverse mode
  • Huge number of longitudinal resonances (300m fiber loop)

leo

firth

Presenter Notes

Semiconductor device with coherent forcing

Theoretically

  • Not much done about purely longitudinal localized states
  • Three-D light bullets have been observed only in an "unrealistic" limit of fast medium (Brambilla et al PRL (2004))
  • Slow material prevents nontrivial temporal modulations Columbo et al EPJD (2006))
  • Ring configuration required since colliding solitons may cancel each other

Experimentally

  • No experiment dedicated to temporal localized states yet
  • But very interesting experiment about all optical mode-locking

Presenter Notes

Semiconductor device with coherent forcing

All optical mode locking of a semiconductor laser by optical injection: injection at the center frequency between two longitudinal modes leads to a four-wave mixing with mode 'm' forcing mode 'm-1'.

kasuya kasuya

Kasuya et al, Appl. Phys. Lett. 1999

Presenter Notes

One possible approach to temporal cavity solitons in semiconductors:

  • Ring laser
  • Fast medium (class A regime)
  • Optical injection

Strengths:

  • Gain (saturable nonlinearity) implies smaller optical power injection
  • Real time detection
  • Possibility to go to 1+1D or even 3D

Presenter Notes

Experimental system

Presenter Notes

Semiconductor ring laser

ring

  • Carrier lifetime: typically \(\approx 0.1~\)ns
  • Cavity length: \(\approx 1\)~m, roundtrip time \(\approx 3.5~\)ns \(\Rightarrow\) Class A (Tierno et al, Opt. Lett. (2012))
  • Reflectivities: \(\approx 99\%, 10\%\), Finesse (assuming perfect coupling) \(\approx 60\) (Leo et al Nat. Phot. (2010) finesse 24)
  • Emitted power \(\approx 5~\)mW

Presenter Notes

Semiconductor ring laser with optical injection

inj

  • Operating regime: \(1-1.1 ~I_{th}\), lasing regime
  • Injected power reaching the nonlinear element: \(\approx 10~\)mW
  • Detuning parameter :
    • coarse setting via diffraction grating (close to semiconductor gain peak)
    • fine setting via sub-wavelength ring cavity length adjustment

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Observations

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Directionality

Without optical injection, ring laser can operate in clockwise or counterclockwise emission:

inj

Bidirectional emission state can be stable (in general not CW):

  • coupling between both directions
  • spatial segregation (Tierno et al, IEEE J. Sel. Top. Quant. Electron. (2013))

Presenter Notes

Directionality

inj

Optical injection can set directional operation

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Resonances

inj

Weak optical injection shows multiple longitudinal resonances

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Time series