Research
Laser Development

Laser Development

For most of our research projects lasers are needed that are not commercially available. Therefore some of our time is spent developing new techniques or improving existing lasers.

Working areas

  • External cavity diode lasers
  • Cw lasers
  • Pulsed lasers
  • Cw and pulsed fiber amplifiers
  • Laser design software

General setup of the ECDL with polarization locking

Modehop free tuning over 105 GHz using Piezo-Current locking

Modehop free tuning over 130 GHz using Temperature-Piezo Locking

ECDL development

Polarization Locked Tuning of an ECDL

We demonstrated tuning control of an external cavity diode laser employing a non-AR coated diode enabled mode-hop free tuning up to a tuning range of 130 GHz.

History

Practical tests of the Opens internal link in current windowNO sensor showed that the principle of the sensor works. However, due to the limitations in the scanning of the ECDL caused by the acoustically and vibrationally challenging environment, the sensitivity was limited. Therefore we concentrated on ways to extend the mode-hop free tuning range of ECDLs in general. Obviously such systems have a large number of possible applications.

References

  • Thorsten Führer, Sabine Euler and Thomas Walther, Model for tuning an external-cavity diode laser by polarization locking, Opens external link in new windowJ Opt. Soc. Am. B 28 (2011) 508-514
  • Thorsten Führer, Denise Stang and Thomas Walther, Actively controlled tuning of an external cavity diode laser by polarization spectroscopy, Opens external link in new windowOptics Express 17 (2009) 4991-4996
  • Thorsten Führer and Thomas Walther, Extension of the mode-hop free tuning range of an External Cavity Diode Laser Based on a Model of the Mode-hop Dynamics, Optics Letter 33 (2008) 372-374

Injection locked cw Ti:Sapphire

We demonstrated an injection locked, single-mode, cw ring-Ti:Sapphire laser pumped by a solid-state, diode pumped green laser.

Reference

Th. Amthor, M. Sinther und Th. Walther, An injection-seeded, single-mode continuous wave Ti:sapphire laser, Laser Physics Letters 3 (2006) 75-78

Setup

Intensity

Output Spectrum

We have developed an injection seeded, pulsed Ti:saphire laser generating near Fourier-Transfrom limited pulses in the ns-regime. Due to its excellent beam profile, narrow linewidth very high conversion efficiencies in the second-, third- and fourth harmonic can be achieved. Furthermore, since the laser has a short cavity it features a very stable and relatively short build-up time. Therefore non-linear frequency generation such as sum frequency and difference frequency generation with the pump radiation of 532 nm and its fundamental at 1064 nm can be achieved. Thus, the laser system is capable of covering a spectral range of 190 nm to 6000 nm.

Reference

D. Depenheuer, J. Kohl-Landgraf, H. Gläßer, Th. Walther, A pulsed laser system with large spectral coverage by nonlinear frequency conversion appeared online Applied Physics B (2009)

Setup of the injection seeded Ti:saphire laser featuring a triangular cavity and enabling various non-linear frequency conversion schemes.

Time-averaged frequency spectrum of the output recorded by a slowly scanning Fabry-Perot interferometer

Build-up time as a function of wave length.

Total spectral coverage possible.

Dual Frequency Ti:Sapphire Laser

References

  • C. Tian, Th. Walther, R. Nicolaescu, X.J. Pan, Y. Liao and E.S. Fry, Synchronous, dual-wavelength, injection-seeded amplification of 5 ns pulses in a flashlamp-pumped Ti:sapphire laser, Opt. Lett. 24 (1999) 1496-1498

CW Nd-doped fiber amplifiers

We demonstrated amplifying the output of a MISER to several Watt power without increasing its line width.

References

Output power as a function of pump power. The output power was limited by the available pump power.

Spectra of the output of the fiber amplifier. (a) broadband spectrum (b) Spectrum of scanning Fabry-Perot interferometer (the inset shows the spectrum of the MISER) (c) Heterodyne beat note from output with second MISER

CW Yb-doped fiber amplifiers

Operation of a two-staged Yb-doped fiber amplifier down to 1014.8 nm was demonstrated. In order to overcome ground state absorption at the signal wavelength the fiber was cooled down to liquid nitrogen temperatures.

References

Albert Seifert, Mathias Sinther, Thomas Walther, Edward S. Fry, Narrow-linewidth, multi-Watt Yb:doped fiber amplifier at 1014.8 nm, Opens external link in new windowAppl. Opt. 45 (2006) 7908

Effect of cooling in the absorption cross-section

Broadband output spectra of the two stages of our fiber amplifier.

Pulsed Fiber Amplifier

A three stage Yb-doped fiber amplifier exhibiting Fourier-transform limited pulses in the ns-regime has been demonstrated. The power was limited by the onset of stimulated Brillouin scattering. A careful optimization of fiber parameters was necessary in order to achieve the energy levels in question.

References

Kai Schorstein and Thomas Walther, A high spectral brightness Fourier transform limited nanosecond Yb-doped fiber amplifier, Applied Physics B 97 (2009)591

Peak power and energy per pulse as a function of the pulse duration for the second stage. The power was limited by the onset of stimulated Brillouin scattering (SBS).

Output energy of the third stage at the fundamental and after SHG. Again the energy was limited by the onset of SBS

CW Type-II Second Harmonic Generation without Temperature Control

Setup of the build-up cavity. By placing a lambda/2 plate inside the cavity, the cavity is only closed after the second round trip.

References

  • Y. Emery, A. Fleischhauer, Th. Walther and E.S. Fry, Angle Tuned, type-II, external cavity frequency doubling without temperature stabilization, Appl. Opt. 38 (1999) 972

CW Type-I Second Harmonic Generation

We routinely frequency double and quadruple (via two consecutive SHG) the output radiation of our home built laser systems such as fiber amplified ECDL sources.

Efficiency and Output Power of our fiber amplified ECDL at 1028 nm frequency doubled to 514 nm (left) Latest generation of our SHG cavities - in this case it is a build up cavity for 870 nm light and a KNbO3 crystal.

 

Pulsed SHG/THG/FHG

By a customized, very compact design of our frequency conversion unit we achieved high conversion efficiencies for second harmonic, third harmonic and fourth harmonic generation. Dual-wave plates (acting as lambda waveplates for the fundamental and lambda/2-plates for the harmonic) are placed in between non-linear crystals in order to use type-I processes in each step.

References

  • T. Beck, Master Thesis, Darmstadt, 2009
  • C. Tian, Th. Walther, R. Nicolaescu, X.J. Pan, Y. Liao and E.S. Fry, Synchronous, dual-wavelength, injection-seeded amplification of 5 ns pulses in a flashlamp-pumped Ti:sapphire laser, Opt. Lett. 24 (1999) 1496-1498
  • D. Depenheuer, J. Kohl-Landgraf, H. Gläßer, Th. Walther, A pulsed laser system with large spectral coverage by nonlinear frequency conversion, appeared Applied Physics B (2009)

JLaserLab 2.0

JLaserLab is a platform independent GUI based resonator design software based on the ABCD matrix formalism. Development goals of JLaserLab are

  • Ease of use
  • Platform independence
  • intuitive user interface

We therefore opted for a program with graphical user interface based on the language Java.

Feature List

  • Easy Design of linear/ring resonators
  • 3D-Engine for 3D representation of resonator
  • ABCD matrix formalismn
  • Real-time calculation of beam waist, cavity setup
  • Stability analysis
  • Easy adjust feature of elements
  • Ray tracing of prism expanders etc.

Wish List (to be added at some point)

  • Custom elements
  • Automatic calculation of mode-matching
  • Improvement of performance

Input window of JLaserLab

Output of JLaserLab for the cavity of the right

Laser Diode Current Controller LQprO

Within our work on laser development we have developed a laser diode current controller. There are two versions:

  • An ultra-low noise current controller (up to 140 mA)
  • A low-noise current controller (up to 400 mA)

Feature List

  • Low noise
  • Stable operation
  • Modulation capabilities
  • Slow modulation over full scale
  • Simultaneous slow/fast modulation
  • Suitable for Pound-Drever-Hall stabilization
  • Four layer board SMD technology
  • Other currents/voltages upon request
  • 19'' Rack assembly incl. power supply available

Data Sheet (opens in new tab)

Please contact for more details.