1. Femtosecond laser pulse phenomena

Development of fs sources

This group was one of the first to recognize the essential role of dispersion in femtosecond laser cavities, and to achieve intracavity pulse compression with prisms [W. Dietel, J.J. Fontaine and J.-C. Diels, Optics Lett. 8, 4-6 (1983)],   leading to 60 fs pulses, the world record in the early 80's.

Frequency combs, autostabilization

After an experimental demonstration that the modes of the mode-locked laser are equally spaced [1], we realized active (electronic) stabilization of frequency combs to a ULE reference cavity [2]. Further efforts thrived at moving away from electronic feedback loops. A theory of intracavity coherent interaction showed the possibility of auto-stabilization of a frequency comb [3]. Another method of autostabilization of an intracavity synchroneously pumped optical parametric oscillator was devised, based on opposite chirp of pump and signal [4]. Finally, purely optical coupling is substituted to the electronic loop to lock the modes of a frequency comb to those of a glass etalon [5].

References

  1. R. J. Jones, J. C. Diels, J. Jasapara, and W. Rudolph. Stabilization of the frequency, phase, and repetition rate of an ultra-short pulse train to a Fabry-Perot reference cavity. Optics Comm., 175:409-418, (2000).
  2. R. J. Jones and J. C. Diels. Stabilization of femtosecond lasers for optical frequency metrology and direct optical to radio frequency synthesis. Phys. Rev. Lett., 86:3288-3291, (2001).
  3. Ladan Arissian, Jean-Claude Diels, and Andreas Velten. Dark line resonance in Rb87 for auto-stabilization of the repetition rate.  CLEO'2006, Long Beach, CA, (2006)
  4. Xuan Luo, Ning Hsu, Jens Biegert, and Ladan Arissian. Pulse compression in parametric amplification. Cassandra Strickland, editor, Wiley Encyclopedia of Electrical and Electronics Engineering, in press. Wiley, 2018.
  5. Koji Masuda, James Hendrie, Jean-Claude Diels, and Ladan Arissian. Envelope, group and phase velocities in a nested frequency comb. Journal of Physics B, 49:085402, (2016).

Intracavity Phase Interferometry

Most researchers see the laser as a "black box" producing coherent radiation with which to perform some measurements. We have instead looked at the laser as the most sensitive sensor, if measurements are performed intracavity. In particular, we developed mode-locked lasers in which two ultrashort pulses circulate, to be used as active differential interferometers. The output of these lasers consists in two pulse trains of exactly the same repetition rate, but with a frequency difference proportional to the parameter being "sensed". This is the most sensitive phase sensor in the world, because a phase difference between the two intracavity pulses (caused by some external parameter being sensed) is converted directly into a frequency (the "beat frequency" measured by interfering the two pulse trains on a detector). A review of our work on Intracavity Phase  Interferometry can be found in Photonics Review [L. Arissian and J.-C. Diels. Intracavity phase interferometry: frequency comb sensors inside a laser cavity. Laser & Photonics Rev, 8:799-826, (2014)].

Overview of IPI.pps

Inertial sensors (laser gyro without dead band with ring cavities; accelerometers in the case of linear cavities) are the most obvious applications. We have also demonstrated measurement of changes of index of refraction, linear and nonlinear, with a sensitivity better than 10-8 radians.  The intracavity measurement has also been applied to the measurement of minute backscattering: an intensity backscattering coefficient of less than 10-15 can be resolved.  A new method has recently been devised to enhance the extraordinary phase sensitivity of intracavity phase interferometry by applying a giant dispersion to all modes of the comb [8]. This method is being tested in Ti:Sapphire ring laser, and will be applied to fiber lasers.

Ultrashort pulse measurements in amplitude and phase

Numerous diagnostic methods to analyze the amplitude and phase of the ultrashort pulses have been pioneered, starting with the “interferometric autocorrelation" widely used since its first report in 1980 [1, 2]. The next generation was the “femtonitpicker" [3], multiple and single shot [4]; a forerunner to “Picasso" and “Mosaic", and most recently the pulse “Characterization by Cascading Nonlinearity Inside a Spectrometer” (CaNIS), involving simply a spectrometer and two nonlinear crystals.

References

  1. J.-C. Diels, J. Menders, and H. Sallaba. Generation of coherent pulses of 60 optical cycles through synchronization of the relaxation oscillations of a mode-locked dye laser. In R. M. Hochstrasser, W. Kaiser, and C. V. Shank, editors, Picosecond Phenomena II, page 41, Berlin, 1980. Springer-Verlag.
  2. J.-C. Diels, J. J. Fontaine, I. C. McMichael, and F. Simoni. Control and measurement of ultrashort pulse shapes (in amplitude and phase) with femtosecond accuracy. Applied Optics, 24:1270-1282, (1985).
  3. J.-C. Diels, J. J. Fontaine, N. Jamasbi, Ming Lai, and J.Mackey. The femtonitpicker. CLEO'87, MD3, Baltimore, MD, (1987).
  4. Chi Yan and J.-C. Diels. Amplitude and phase recording of ultrashort pulses. J. of the Opt. Soc. Am. B, 8:1259-1263, 1991.
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