Milestones - Meilensteine

1992: Ge lasers with narrow linewidth of less than 1 MHz in the 2.5 THz range measured with room temperature Schottky diodes
1993: Mesh output coupler used as resonator part with germanium THz laser.
1994: Heterodyne detection of laser modes: frequency temperature tuning.
1994: Single mode emission of germanium THz laser.
1996: Deep acceptor doped germanium THz lasers with high duty cycles.
1996: Simple fabrication of Ge THz lasers by diffusing copper into commercially available pure Ge.
1997: Demonstrated wide tuning range from 1 to 4 THz with a single device (unique 160% bandwidth at 2.5 THz).
1997: First THz semiconductor laser operation in mobile, small foot-print closed-cycle cooler.
1997: With room temperature detection no cryogenic liquid needed.
1999: Planar lasers: simplifies drastically the fabrication of resonators.
2000: Enhanced continuous spontaneous emission indicating continuous wave laser emission for small 0.5 mm³ crystals.
2000: Very high duty cycles up to 5%, low 4 Watt input power and high 45 kHz repetition rates.
2000: Mode-locked copper-doped germanium THz lasers.
2001: High duty cycles of large volume (0.3 cm³) high power (Watt) output lasers in closed-cycle cooler up to 2%.
2001: Simple plug and switch operation. Laser is operational within 30 min after starting the cooler.
2003: First far-infrared and THz multilayer mirrors for broadband and Q-factor resonators.
2005: Fully automated LabView controlled germanium laser spectrometer for aquaeous samples.
2005: Operated with user interface by students from chemistry and biochemistry with low-tech background.
2005: Various spectroscopic sample set-ups: transmission, ATR, cavity enhanced ATR, two-beam.

THz germanium laser system consisting of a Ge:Be laser and a Ge:Al photodetector: 

• E. Bründermann, D.R. Chamberlin, E.E. Haller, High duty cycle and continuous terahertz emission from germanium, Appl. Phys. Lett. 76, 2991-2993 (2000). 
• E. Bründermann et al., Double acceptor doped Ge: A new medium for inter-valence-bandlasers, Appl. Phys. Lett. 68, 3075-3077 (1996).

Recent publications using the THz germanium laser system:

• M. Heyden, E. Bründermann, U. Heugen, G. Niehues,  D. M. Leitner, M. Havenith,
  Long range influence of carbohydrates on the solvation dynamics of water – Answers from THz absorption measurements and molecular modeling simulations,
  J. Am. Chem. Soc. 130 (17), 5772 (2008).


• S. Ebbinghaus, S. J. Kim, M. Heyden, X. Yu, M. Gruebele, D. M. Leitner, M. Havenith,
  Protein sequence- and pH-dependent hydration probed by Terahertz spectroscopy,
  J. Am. Chem. Soc. 130, 2374 (2008).
  "Acknowledgment. We wish to thank E. Bründermann and G. Schwaab for their initial instrument development and many helpful discussions."


• S. Ebbinghaus, S. J. Kim, M. Heyden, X. Yu, U. Heugen, M. Gruebele, D. M. Leitner, M. Havenith,
  An extended dynamical solvation shell around proteins,
  PNAS 104, 20749 (2007).
  "Acknowledgments. We thank E. Bründermann and G. Schwaab for the initial instrument setup, helpful discussions, and software development."


• D.M. Leitner, M. Havenith, and M. Gruebele,
  Biomolecule large amplitude motion and solvation dynamics: Modeling and probes from THz to X-rays,
  Intl. Reviews in Physical Chemistry 25, issue 4, 553-582 (2006).


• U. Heugen, G. Schwaab, E. Bründermann, M. Heyden, X. Yu, D.M. Leitner, and M. Havenith,
  Solute induced retardation of water dynamics probed directly by THz spectroscopy,
  PNAS 103, 12301 (2006).


• E. Bründermann, M. Havenith,
  Applications of semiconductor terahertz lasers in biomolecular spectroscopy and imaging,
  Proc. SPIE 6194, 619406 (2006).


• R. Schiwon, G. Schwaab, E. Bründermann, M. Havenith,
  THz cavity enhanced attenuated total reflection spectroscopy,
  Appl. Phys. Lett. 86, 201116 (2005).


• A. Bergner, U. Heugen, E. Bründermann, G. Schwaab, M. Havenith, D.R. Chamberlin, and E.E. Haller,
  New p-Ge THz spectrometer for the study of solutions: THz absorption spectroscopy of water,
  Rev. Sci. Instr. 76, 063110 (2005).