Nanoscale Spectroscopy and Plasmonics in Infrared

By Mikhail Belkin

University of Texas at Austin

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Abstract

In this talk, I will present the results of two of our research projects. I will start with a simple technique for nanoscale mid-infrared spectroscopy that we have developed recently. Subwavelength resolution is achieved by detecting optical absorption through measuring local photothermal expansion with an atomic force microscope (AFM). Spatial resolution is determined by thermal diffusion length, which is smaller than 50 nm in typical chem/bio samples excited with nanosecond laser pulses. Tunable quantum cascade lasers are used as light sources. To detect minute sample expansions, we moved the repetition rate of the laser pulses in resonance with the AFM cantilever bending frequency and benefited from the resultant resonant enhancement. Plasmonic tip enhancement of light intensity is used to further improve spatial resolution and sensitivity of the technique. We were able to take mid-IR images and vibrational spectra of polymer films as thin as 10 nm with l/170 spatial resolution. The extension of this method to THz spectral range and possible improvements to achieve monolayer sensitivity will also be discussed. In the second part of the talk, I will present the results of our project aimed to develop broadly-tunable monolithic bandpass filters based on unique properties of long-range surface plasmon-polaritons. A small change of the refractive index of the cladding material in these filters may be translated into a large bandpass wavelength shift. We present experimental results with proof-of-principle devices operating at telecom wavelengths in which 0.004 change of the refractive index of the cladding material is translated into 210 nm bandpass tuning.

Bio

Mikhail Belkin Mikhail Belkin received his B.S. degree in Physics and Mathematics from Moscow Institute of Physics and Technology in 1998 and Ph.D. in Physics from the University of California at Berkeley in 2004. From 2004 to 2008 he worked in Federico Capasso's group in the School of Engineering and Applied Sciences at Harvard University, first as a postdoctoral fellow and later as a research associate. He joined the faculty of the University of Texas at Austin in the fall of 2008. Mikhail Belkin's current research interests include the development of novel quantum cascade lasers, giant optical nonlinearities in semiconductor nanostructures, mid-infrared and THz photonic and plasmonic systems for chemical sensing, and metamaterials in mid-infrared. Several of the recent publications he co-authored have received considerable media coverage, in particular his work on THz semiconductor laser sources based on intra-cavity difference-frequency generation (see MIT Technology Review, Laser Focus World, Science Daily, and others), a millimeter-sized mid-infrared spectrometer for chem/bio sensing (see MIT Technology Review, Photonics Spectra, Science Daily, and others), and THz quantum cascade lasers with record operating temperatures (see Optics.ORG).

Cite this work

Researchers should cite this work as follows:

  • Mikhail Belkin (2012), "Nanoscale Spectroscopy and Plasmonics in Infrared," http://nanohub.org/resources/13510.

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Time

Location

Physics, Room 203, Purdue University, West Lafayette, IN

Tags

Nanoscale Spectroscopy and Plasmonics in Infrared
  • Nanoscale Spectroscopy and Plasmonics in Infrared 1. Nanoscale Spectroscopy and Pla… 8.6666666666666661
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  • Background and talk outline 2. Background and talk outline 55.3
    00:00/00:00
  • Outline 3. Outline 127.3
    00:00/00:00
  • Quantum Cascade Lasers 4. Quantum Cascade Lasers 133.43333333333334
    00:00/00:00
  • Motivation 5. Motivation 387.96666666666664
    00:00/00:00
  • NSOM techniques 6. NSOM techniques 516.3
    00:00/00:00
  • Photoexpansion Microscopy 7. Photoexpansion Microscopy 659.2
    00:00/00:00
  • Photoexpansion Microscopy 8. Photoexpansion Microscopy 925.13333333333333
    00:00/00:00
  • Resonance enhancement 9. Resonance enhancement 1056.6666666666667
    00:00/00:00
  • Enhancement analysis 10. Enhancement analysis 1320.5333333333333
    00:00/00:00
  • Experimental Setup 11. Experimental Setup 1373.4
    00:00/00:00
  • Signal Enhancement & Spectroscopy 12. Signal Enhancement & Spectrosc… 1480.8666666666666
    00:00/00:00
  • Simulations 13. Simulations 1673.3666666666666
    00:00/00:00
  • Spatial Resolution 14. Spatial Resolution 1853.7666666666667
    00:00/00:00
  • Sub-wavelength infrared Imaging 15. Sub-wavelength infrared Imagin… 1997.4666666666667
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  • Plasmonic enhancement 16. Plasmonic enhancement 2057.6
    00:00/00:00
  • Plasmonic enhancement: experiment 17. Plasmonic enhancement: experim… 2218.4333333333334
    00:00/00:00
  • Summary 18. Summary 2315.7666666666669
    00:00/00:00
  • Outline 19. Outline 2530.5666666666666
    00:00/00:00
  • Motivation 20. Motivation 2541.1333333333332
    00:00/00:00
  • Long-range surface plasmon polaritons (LR SPP) 21. Long-range surface plasmon pol… 2674.1666666666665
    00:00/00:00
  • LRSPP characteristics 22. LRSPP characteristics 2786
    00:00/00:00
  • Insertion loss of LRSPP waveguide 23. Insertion loss of LRSPP wavegu… 2828.2333333333331
    00:00/00:00
  • Widely-tunable LR SPP bandpass filter 24. Widely-tunable LR SPP bandpass… 2906.8
    00:00/00:00
  • Proof-of-principle device 25. Proof-of-principle device 3118.4
    00:00/00:00
  • Experimental results 26. Experimental results 3208.2333333333331
    00:00/00:00
  • Experimental results 27. Experimental results 3346.6
    00:00/00:00
  • Summary 28. Summary 3462.1333333333332
    00:00/00:00
  • Research group 29. Research group 3520.8666666666668
    00:00/00:00
  • Widely-tunable LR SPP bandpass filter 30. Widely-tunable LR SPP bandpass… 3568.3
    00:00/00:00
  • Experimental results 31. Experimental results 3631.9333333333334
    00:00/00:00
  • Widely-tunable LR SPP bandpass filter 32. Widely-tunable LR SPP bandpass… 3669.5666666666666
    00:00/00:00