Docstoc

Slide 1 - Texas A_M University

Document Sample
Slide 1 - Texas A_M University Powered By Docstoc
					 Towards “on-the-fly” detection
   of Bacterial Endospores
                            by Dmitry Pestov

In collaboration with:
Xi Wang,1 Gombojav O. Ariunbold,1 Robert K. Murawski,1,2
Vladimir A. Sautenkov,1 Arthur Dogariu,2 Alexei V. Sokolov,1
and Marlan O. Scully1,2

1Institute
         for Quantum Studies and Depts. of Physics and Chemical Engineering,
Texas A&M University, College Station, TX 77843
2Applied Physics and Materials Science Group, Eng. Quad.,

Princeton University, Princeton, NJ 08544


         TAMU/Princeton Summer School on Quantum Optics and Molecular Physics
                            Casper, WY, July 15-21, 2007
      Towards “on-the-fly” detection
         of Bacterial Endospores

           Outline:
            What is “Hybrid CARS”?
            Implementation
            Backscattered CARS on B. subtilis spores
            Single-shot Measurements



Dmitry Pestov et al., Towards “on-the-fly” detection…   Slide 2 of 19
Coherent Anti-Stokes Raman Scattering (CARS)

              Energy level diagrams                       CARS, CSRS = pr ± (p- s)

                                   |aj>            |aj>   kCARS, CSRS = kpr ± (kp- ks)


                                                               Sample            4
                                  pr         s                                     3
                                                                                         5
                                                                                     1
                            pr   CARS                                                  2
                 p    s          p         FWM
                                   |bj>            |bj>
                                   |c>             |c>       1 – pump 4 – CARS
                                                             2 – Stokes 5 – CSRS
                        CARS            FWM
                                                             3 – probe

       Problem: Non-resonant four-wave mixing (FWM) as a background and
       fluctuations associated with it.

Dmitry Pestov et al., Towards “on-the-fly” detection…                       Slide 3 of 19
                      Hybrid CARS Technique
          Frequency domain                                         Time domain
                                                                   Time domain




       Science 316, 13 April 2007, p. 265.      Sukesh Roy et al. (Innovative Scientific Solutions),
  Efficient broadband excitation and frequency-resolved probing, multi-channel detection
                                                Appl. Phys. Lett. 87 (2005), 264103
 => comprehensive species-specific information.
                                                 → Combustion diagnostics
  The technique is relatively insensitive to signal amplitude fluctuations.
                                                Benjamin D. Prince et al. (Iowa State University),
  Straightforward elimination of the non-resonant of Chemical Physics 125 (2006), 044502
                                                Journal background.
                                                 → Dynamics of vibrational energy flow
Dmitry Pestov et al., Towards “on-the-fly” detection…                                Slide 4 of 19
              Hybrid CARS is a combination of…
     Broadband/Multiplex CARS                                  Time-Resolved CARS




 Klick et al., Applied Optics 20, 1178 (1981)       Leonhardt et al., Chem. Phys. Lett. 133, 373 (1987)
 Voroshilov, J. Chem. Phys. 106, 2589 (1997)        Wen et al., J. Opt. Soc. Am. B 8, 813 (1991)
 Muller et al., J. Phys. Chem. B 106, 3715 (2002)   Materny et al., Appl. Phys. B 71, 299 (2000)
 Knee et al., Opt. Lett. 29, 2701 (2004)            Volkmer et al., Appl. Phys. Lett. 80, 1505 (2002)
 Petrov et al., Opt. Express 13, 1299 (2005)        Pestov et al., J. Raman Spectr. 37, 392 (2006)
 Rinia et al., J. Phys. Chem. B 110, 4472 (2006)    Lucht et al., Appl. Phys. Lett. 89, 251112 (2006)

Dmitry Pestov et al., Towards “on-the-fly” detection…                                  Slide 5 of 19
        Discrimination between CARS and FWM
  The non-resonant and Raman resonant contributions into the nonlinear
  polarization can be written as:
                
     P ( ) ~  d NR) E probe (  )  S (),
      ( 3)
      NR
                    (3
                                                                         E = electric field
                 0                                                       ω = field frequency
                
                                  j                                     ΩRj = j-th Raman
     P ( ) ~  d
       ( 3)
                                              E probe (  )  S (),
      R
                 0      j    Rj    i j                              frequency
                                                                        Γj = j-th Raman
     where : S ()   d ' E pump ( ' )EStokes ( ').
                                          
                                                                         line width
                        0
                                       2             2            2
     I CARS  PNR) ( )  PR( 3) ( )  PNR) ( )  PR( 3) ( )  2 Re( PNR) ( ) PR( 3) ( ))
               (3                        (3                              (3            *




 Since the pump-Stokes convolution, S(), is a smooth function, it produces a
 broadband FWM spectrum even for a sharp-peaked probe spectrum. On the other
 hand, the Raman resonance contribution results in a narrow spectral peak whose
 width is determined by the Raman line width or the probe spectral width,
 whichever is greater.
Dmitry Pestov et al., Towards “on-the-fly” detection…                                Slide 6 of 19
        Sodium Dipicolinate Powder (NaDPA)




                                                        Fig. Spontaneous
                                                        Raman spectrum
                                                        of NaDPA powder.
                                                        Excitation – at 532 nm.




         NaDPA is an easy-to-make substitute for CaDPA present in spores.

Dmitry Pestov et al., Towards “on-the-fly” detection…                   Slide 7 of 19
               Backscattered CARS on NaDPA
                                                                         Parameters:
                                                                         Pump
                                                                         712-742 nm,
                                                                         2.0 J/pulse

                                                                         Stokes
                                                                         803 nm,
                                                                         3.9 J/pulse

                                                                         Probe
                                                                         577.9 nm,
                                                                         FWHM~0.7 nm
                                                                         ~0.5 J/pulse




                                                    D. Pestov et al, Science 316, 265 (2007).

Dmitry Pestov et al., Towards “on-the-fly” detection…                        Slide 8 of 19
               Backscattered CARS on NaDPA
                                                                         Parameters:
                                                                         Pump
                                                                         712-742 nm,
                                                                         2.0 J/pulse

                                                                         Stokes
                                                                         803 nm,
                                                                         3.9 J/pulse

                                                                         Probe
                                                                         577.9 nm,
                                                                         FWHM~0.7 nm
                                                                         ~0.5 J/pulse




                                                    D. Pestov et al, Science 316, 265 (2007).

Dmitry Pestov et al., Towards “on-the-fly” detection…                        Slide 9 of 19
                      Experimental Implementation
                                         Pump laser
                                                                        Backscattering geometry
   Regenerative amplifier                (Evolution)
   ~1 mJ/pulse, 1 kHz rep.rate, 40 fs                      DS1 M1                            M2
             (Legend)                     Oscillator
                                           (Mira)                                BPF+SPF
                                                                                                  L5
                                                                          L4
          OPA1
                                                Slit                             Sample
                                                                   L3
                                                                                    Spectrometer
                                                                           CCD    (Chromex-250is)
          OPA1                          G1 L1          L2 G2 DS2


              BS – beamsplitter, DS1,2 – delay stages, BPF+SPF – a set of
              band-pass and short-pass filters, L1-5 - lenses, G1,2 – gratings,
              M1,2 – alignment mirrors, CCD-charge coupled device.


Dmitry Pestov et al., Towards “on-the-fly” detection…                                      Slide 10 of 19
                     Bacillus Subtilis Spores




        The image is a Scanning electron Micrograph taken using a JEOL JSM 6400
        SEM at the Microscopy and Imaging Center, Texas A&M University.


Dmitry Pestov et al., Towards “on-the-fly” detection…                      Slide 11 of 19
                   Bacillus Subtilis Spores
                spontaneous Raman measurements
Esposito et al, Appl. Spec. 57, p. 868 (2003)   Nelson et al, Appl. Spec. 58, p. 1408 (2004)




                                                 Fig.2: UV resonance Raman spectrum of
                                                 B. subtilis endospores in 0.100 M sodium
                                                 sulfate excited by 244 nm light.

                                                 Fig. 1: Raman spectra of individual Bacillus
                                                 spores obtained with 488 nm excitation.


Dmitry Pestov et al., Towards “on-the-fly” detection…                           Slide 12 of 19
       Hybrid CARS on Bacillus Subtilis Spores




Dmitry Pestov et al., Towards “on-the-fly” detection…   Slide 13 of 19
       Hybrid CARS on Bacillus Subtilis Spores:
        probe bandwidth/delay optimization
 Integration time – 1 s per step (200 ms5 sampl.)




Dmitry Pestov et al., Towards “on-the-fly” detection…   Slide 14 of 19
       Hybrid CARS on Bacillus Subtilis Spores:
        probe bandwidth/delay optimization
 Integration time – 1 s per step (200 ms5 sampl.)




Dmitry Pestov et al., Towards “on-the-fly” detection…   Slide 15 of 19
  Setup Parameters for Single-shot Measurements

    Pump
    ~1250 nm, <16 J/pulse
    Beam diameter dFWHM  36 m (focused with a 20-cm lens).

    Stokes
    ~1550 nm, <13 J/pulse
    Beam diameter dFWHM  43 m (focused with a 20-cm lens).

    Probe
    ~806 nm, <3.2 J/pulse, FWHM  30 cm-1.
    Beam diameter dFWHM  32 m (focused with a 10-cm lens).



Dmitry Pestov et al., Towards “on-the-fly” detection…    Slide 16 of 19
       Hybrid CARS on Bacillus Subtilis Spores:
              single-shot measurements




       Pump - p = 1.25 m, 4 J/pulse; probe - pr = 805.8 nm, 3 J/pulse;
       Stokes - s = 1.54 m, 4 J/pulse (a); s = 1.56 m, 4 J/pulse (b).
       Estimated sample volume – 104 spores.
Dmitry Pestov et al., Towards “on-the-fly” detection…                 Slide 17 of 19
       Hybrid CARS on Bacillus Subtilis Spores:
              single-shot measurements




Dmitry Pestov et al., Towards “on-the-fly” detection…   Slide 18 of 19
                       Take-Home Message

       Hybrid CARS is a promising technique for detection
       applications. In particular, we showed that it can be used for
       bacterial spore detection in the backscattering configuration.
       From our experiments, the major Raman lines of B. subtilis
       spores (~104 of them) in the fingerprint region can be detected
       in a few shots.


       $$ Support: the Office of Naval Research under Award No.
       N00014-03-1-0385, DARPA, NSF (Grant No.PHY-0354897),
       an Award from Research Corporation, and the Robert A.
       Welch Foundation (Grants No. A-1261 and A-1547).

Dmitry Pestov et al., Towards “on-the-fly” detection…         Slide 19 of 19

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:6
posted:7/30/2011
language:English
pages:19