Mid-infrared Frequency Comb Spanning an Octave Based on an Er Fiber Laser and Difference-Frequency Generation

We describe a coherent mid-infrared continuum source with 700 cm-1 usable bandwidth, readily tuned within 600–2500 cm-1 (4–17 μm) and thus covering much of the infrared "fingerprint" molecular vibration region. It is based on nonlinear frequency conversion in GaSe using a compact commercial 100-fs-pulsed Er fiber laser system providing two amplified near-infrared beams, one of them broadened by a nonlinear optical fiber. The resulting collimated mid-infrared continuum beam of 1 mW quasi-cw power represents a coherent infrared frequency comb with zero carrier-envelope phase, containing about 500,000 modes that are exact multiples of the pulse repetition rate of 40 MHz. The beam's diffraction-limited performance enables long-distance spectroscopic probing as well as maximal focusability for classical and ultraresolving near-field microscopies. Applications are foreseen also in studies of transient chemical phenomena even at ultrafast pump-probe scale, and in high-resolution gas spectroscopy for e.g. breath analysis.

[1]  Ingmar Hartl,et al.  Widely-tunable mid-infrared frequency comb source based on difference frequency generation. , 2012, Optics letters.

[2]  Xian Liu,et al.  Free-space optics optimization models for building sway and atmospheric interference using variable wavelength , 2009, IEEE Transactions on Communications.

[3]  F. Keilmann,et al.  Spectroscopic near-field microscopy using frequency combs in the mid-infrared. , 2006, Optics express.

[4]  J W Nicholson,et al.  Direct-comb molecular spectroscopy with accurate, resolved comb teeth over 43 THz. , 2012, Optics letters.

[5]  P. Nguyen,et al.  Real time observation of ultrafast peptide conformational dynamics: molecular dynamics simulation vs infrared experiment. , 2011, The journal of physical chemistry. B.

[6]  M. Schubert,et al.  Infrared dielectric functions and phonon modes of high-quality ZnO films , 2003 .

[7]  Roberta Ramponi,et al.  Mid-infrared optical combs from a compact amplified Er-doped fiber oscillator. , 2008 .

[8]  E. Korte,et al.  Infrared Spectroscopic Ellipsometry , 2006 .

[9]  F. Keilmann,et al.  Broadband-infrared assessment of phonon resonance in scattering-type near-field microscopy , 2011 .

[10]  F. Keilmann,et al.  Nano-FTIR absorption spectroscopy of molecular fingerprints at 20 nm spatial resolution. , 2012, Nano letters.

[11]  F. Keilmann,et al.  Near-field microscopy by elastic light scattering from a tip , 2004, Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences.

[12]  Eberhard Riedle,et al.  Tunable sub-10-fs ultraviolet pulses generated by achromatic frequency doubling. , 2004, Optics letters.

[13]  Yusuke Kajihara,et al.  Nano-FTIR chemical mapping of minerals in biological materials , 2012, Microscopy and Microanalysis.

[14]  Jun Ye,et al.  Phase-stabilized, 1.5 W frequency comb at 2.8-4.8 microm. , 2009, Optics letters.

[15]  Ingmar Hartl,et al.  Widely-tunable mid-IR frequency comb source based on difference frequency generation , 2012 .

[16]  P. Schunemann,et al.  Mid-IR frequency comb source spanning 4.4-5.4 μm based on subharmonic GaAs optical parametric oscillator. , 2011, Optics letters.

[17]  S. Corzine,et al.  Widely tunable mode-hop free external cavity quantum cascade lasers for high resolution spectroscopy and chemical sensing , 2008 .

[18]  F. Keilmann,et al.  Antenna-mediated back-scattering efficiency in infrared near-field microscopy. , 2008, Optics express.

[19]  Fritz Keilmann,et al.  Time-domain mid-infrared frequency-comb spectrometer. , 2004, Optics letters.

[20]  Paul Dumas,et al.  Chemical imaging of biological tissue with synchrotron infrared light. , 2006, Biochimica et biophysica acta.

[21]  Albert Schliesser,et al.  Mid-infrared frequency combs , 2012, Nature Photonics.

[22]  Tom Gardiner,et al.  Asynchronous midinfrared ultrafast optical parametric oscillator for dual-comb spectroscopy. , 2012, Optics letters.

[23]  A. Zayats,et al.  Nano-optics and near-field optical microscopy , 2009 .

[24]  Nanoscale Chemical Mapping by Local Infrared Spectroscopy (nano-FTIR) , 2012, Microscopy Today.

[25]  R. Holzwarth,et al.  Mid-Infrared Optical Frequency Combs based on Crystalline Microresonators , 2011, 1109.2716.

[26]  Markus Brehm,et al.  Frequency-comb infrared spectrometer for rapid, remote chemical sensing. , 2005, Optics express.

[27]  A. A. Anappara,et al.  Sub-cycle switch-on of ultrastrong light–matter interaction , 2009, Nature.

[28]  P. Griffiths.  Fourier Transform Infrared Spectrometry , 2007 .

[29]  Ingmar Hartl,et al.  Octave-spanning ultrafast OPO with 2.6-6.1 µm instantaneous bandwidth pumped by femtosecond Tm-fiber laser. , 2012, Optics express.

[30]  Xinjin Cao,et al.  A review of laser welding techniques for magnesium alloys , 2006 .

[31]  R. Butcher,et al.  Slow molecule detection or Ramsey fringes in two-photon spectroscopy: which is better for high resolution spectroscopy and metrology ? , 1999, Optics express.

[32]  T. Hänsch,et al.  Optical frequency metrology , 2002, Nature.