Abstract

We demonstrate microfluidic laser intra-cavity absorption spectroscopy with mid-infrared λ≈9µm quantum cascade lasers. A deep-etched narrow ridge waveguide laser is placed in a microfluidic chamber. The evanescent tails of the laser mode penetrate into a liquid on both sides of the ridge. The absorption lines of the liquid modify the laser waveguide loss, resulting in significant changes in the laser emission spectrum and the threshold current. A volume of liquid as small as ~10pL may, in principle, be sufficient for sensing using the proposed technique. This method, similar to the related gas-phase technique, shows promise as a sensitive means of detecting chemicals in small volumes of solutions.

© 2007 Optical Society of America

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  1. L. Diehl, D. Bour, S. Corzine, J. Zhu, G. Hofler, M. Loncar, M. Troccoli, and F. Capasso, "High-power quantum cascade lasers grown by low-pressure metal organic vapor-phase epitaxy operating in continuous wave above 400 K," Appl. Phys. Lett. 88, 201115 (2006).
    [CrossRef]
  2. F. Capasso, C. Gmachl, D. L. Sivco, and A. Y. Cho, "Quantum cascade lasers," Phys. Today 55, 34-40 (2002).
    [CrossRef]
  3. D. Lin-Vien, N. B. Colthup, W. G. Fateley, and J. G. Grasselli, The Handbook of Infrared and Raman Characteristic Frequencies of Organic Molecules (Academic Press, Boston, MA 1991).
  4. A. Kosterev and F. Tittel, "Chemical sensors based on quantum cascade lasers," IEEE J. Quantum Electron. 38, 582-591 (2002).
    [CrossRef]
  5. C. Charlton, F. de Melas, A. Inberg, N. Croitoru, and B. Mizaikoff, "Hollow-waveguide gas sensing with room-temperature quantum cascade lasers, "IEE Proc.: Optoelectron. 150, 306-309 (2003)
    [CrossRef]
  6. B. Lendl, J. Frank, R. Schindler, A. Müller, M. Beck, and J. Faist, "Mid-infrared quantum cascade lasers for flow injection analysis," Anal. Chem. 72, 1645 (2000).
    [CrossRef] [PubMed]
  7. J. Chen, Z. Liu, C. Gmachl, and D. Sivco, "Silver halide fiber-based evanescent-wave liquid droplet sensing with room temperature mid-infrared quantum cascade lasers," Opt. Express 13, 5953-5960 (2005).
    [CrossRef] [PubMed]
  8. C. Charlton, A. Katzir, and B. Mizaikoff, "Infrared evanescent field sensing with quantum cascade lasers and planar silver halide waveguides," Anal. Chem. 77, 4398-4403 (2005).
    [CrossRef] [PubMed]
  9. C. Charlton, M. Giovannini, J. Faist, B. Mizaikoff, "Fabrication and characterization of molecular beam epitaxy grown thin-film GaAs waveguides for mid-infrared evanescent field chemical sensing," Anal. Chem. 78, 4224-4227 (2006).
    [CrossRef] [PubMed]
  10. S. Schaden, A. Domínguez-Vidal, and B. Lendl, "Quantum cascade laser modulation for correction of matrix-induced background changes in aqueous samples," Appl. Phys. B 86, 347-351 (2007).
    [CrossRef]
  11. V. M. Baev, T. Latz, and P. E. Toschek, "Laser intracavity absorption spectroscopy," Appl. Phys. B 69, 171-202 (1999).
    [CrossRef]
  12. D. Erickson and D. Li, "Integrated microfluidic devices," Anal. Chim. Acta 507, 11-26 (2004).
    [CrossRef]
  13. D. Psaltis, S. R. Quake, and C. Yang, "Developing optofluidic technology through the fusion of microfluidics and optics," Nature 442, 381-386 (2006).
    [CrossRef] [PubMed]
  14. C. Monat, P. Domachuk, and B. J. Eggleton, "Integrated optofluidics: a new river of light," Nat. Photonics. 1, 106-114 (2007).
    [CrossRef]
  15. E. Verpoorte, "Chip vision - optics for microchips," Lab Chip 3, 42N-52N (2003).
  16. L. Diehl, B.G. Lee, P. Behroozi, M. Lončar, M. A. Belkin, F. Capasso, T. Aellen, D. Hofstetter, M. Beck, and J. Faist, "Microfluidic tuning of distributed feedback quantum cascade lasers," Opt. Express 14, 11660-11667 (2006).
    [CrossRef] [PubMed]
  17. E. Verpoorte, A. Manz, H. Lüdi, A.E. Bruno, F. Maystre, B. Krattiger, H. M. Widmer, B.H. van der Schoot, and N.F. de Rooij, "A silicon flow cell for optical detection in miniaturized total chemical analysis systems," Sens. Actuators B 6, 66-70 (1992).
    [CrossRef]
  18. K. B. Mogensen, N. J. Petersen, J. Hübner, and J. P. Kutter, "Monolithic integration of optical waveguides for absorbance detection in microfabricated electrophoresis devices," Electrophoresis 22, 3930-3938 (2001).
    [CrossRef] [PubMed]
  19. J. C. Galas, C. Peroz, Q. Kou, and Y. Chen, "Microfluidic dye laser intracavity absorption," Appl. Phys. Lett 89, 224101 (2006).
    [CrossRef]
  20. J. Faist, M. Beck, T. Aellen, and E. Gini, "Quantum-cascade lasers based on bound-to-continuum transition," Appl. Phys. Lett. 78, 147-149 (2001).
    [CrossRef]
  21. R. Maulini, M. Beck, J. Faist, and E. Gini, "Broadband tuning of external cavity bound-to-continuum quantum-cascade lasers," Appl. Phys. Lett. 84, 1659-1661 (2004).
    [CrossRef]
  22. M. Lončar, B.G. Lee, L. Diehl, M. Belkin, F. Capasso, M. Giovannini, J. Faist, and E. Gini, "Design and fabrication of photonic crystal quantum cascade lasers for optofluidics," Opt. Express 15, 4499-4514 (2007).
    [CrossRef] [PubMed]
  23. M. Beck, D. Hofstetter, T. Aellen, J. Faist, U. Oesterle, M. Ilegems, E. Gini, H. Melchior "Continuous wave operation of a mid-infrared semiconductor laser at room temperature," Science 295, 301-305 (2002).
    [CrossRef] [PubMed]
  24. J. Z. Chen, Z. Liu, Y. S. Rumala, D. L. Sivco, and C. F. Gmachl, "Direct liquid cooling of room-temperature operated quantum cascade lasers," Electron. Lett. 42, 534-535 (2006).
    [CrossRef]

2007

S. Schaden, A. Domínguez-Vidal, and B. Lendl, "Quantum cascade laser modulation for correction of matrix-induced background changes in aqueous samples," Appl. Phys. B 86, 347-351 (2007).
[CrossRef]

C. Monat, P. Domachuk, and B. J. Eggleton, "Integrated optofluidics: a new river of light," Nat. Photonics. 1, 106-114 (2007).
[CrossRef]

M. Lončar, B.G. Lee, L. Diehl, M. Belkin, F. Capasso, M. Giovannini, J. Faist, and E. Gini, "Design and fabrication of photonic crystal quantum cascade lasers for optofluidics," Opt. Express 15, 4499-4514 (2007).
[CrossRef] [PubMed]

2006

J. C. Galas, C. Peroz, Q. Kou, and Y. Chen, "Microfluidic dye laser intracavity absorption," Appl. Phys. Lett 89, 224101 (2006).
[CrossRef]

J. Z. Chen, Z. Liu, Y. S. Rumala, D. L. Sivco, and C. F. Gmachl, "Direct liquid cooling of room-temperature operated quantum cascade lasers," Electron. Lett. 42, 534-535 (2006).
[CrossRef]

C. Charlton, M. Giovannini, J. Faist, B. Mizaikoff, "Fabrication and characterization of molecular beam epitaxy grown thin-film GaAs waveguides for mid-infrared evanescent field chemical sensing," Anal. Chem. 78, 4224-4227 (2006).
[CrossRef] [PubMed]

L. Diehl, B.G. Lee, P. Behroozi, M. Lončar, M. A. Belkin, F. Capasso, T. Aellen, D. Hofstetter, M. Beck, and J. Faist, "Microfluidic tuning of distributed feedback quantum cascade lasers," Opt. Express 14, 11660-11667 (2006).
[CrossRef] [PubMed]

D. Psaltis, S. R. Quake, and C. Yang, "Developing optofluidic technology through the fusion of microfluidics and optics," Nature 442, 381-386 (2006).
[CrossRef] [PubMed]

L. Diehl, D. Bour, S. Corzine, J. Zhu, G. Hofler, M. Loncar, M. Troccoli, and F. Capasso, "High-power quantum cascade lasers grown by low-pressure metal organic vapor-phase epitaxy operating in continuous wave above 400 K," Appl. Phys. Lett. 88, 201115 (2006).
[CrossRef]

2005

J. Chen, Z. Liu, C. Gmachl, and D. Sivco, "Silver halide fiber-based evanescent-wave liquid droplet sensing with room temperature mid-infrared quantum cascade lasers," Opt. Express 13, 5953-5960 (2005).
[CrossRef] [PubMed]

C. Charlton, A. Katzir, and B. Mizaikoff, "Infrared evanescent field sensing with quantum cascade lasers and planar silver halide waveguides," Anal. Chem. 77, 4398-4403 (2005).
[CrossRef] [PubMed]

2004

D. Erickson and D. Li, "Integrated microfluidic devices," Anal. Chim. Acta 507, 11-26 (2004).
[CrossRef]

R. Maulini, M. Beck, J. Faist, and E. Gini, "Broadband tuning of external cavity bound-to-continuum quantum-cascade lasers," Appl. Phys. Lett. 84, 1659-1661 (2004).
[CrossRef]

2003

E. Verpoorte, "Chip vision - optics for microchips," Lab Chip 3, 42N-52N (2003).

C. Charlton, F. de Melas, A. Inberg, N. Croitoru, and B. Mizaikoff, "Hollow-waveguide gas sensing with room-temperature quantum cascade lasers, "IEE Proc.: Optoelectron. 150, 306-309 (2003)
[CrossRef]

2002

F. Capasso, C. Gmachl, D. L. Sivco, and A. Y. Cho, "Quantum cascade lasers," Phys. Today 55, 34-40 (2002).
[CrossRef]

A. Kosterev and F. Tittel, "Chemical sensors based on quantum cascade lasers," IEEE J. Quantum Electron. 38, 582-591 (2002).
[CrossRef]

M. Beck, D. Hofstetter, T. Aellen, J. Faist, U. Oesterle, M. Ilegems, E. Gini, H. Melchior "Continuous wave operation of a mid-infrared semiconductor laser at room temperature," Science 295, 301-305 (2002).
[CrossRef] [PubMed]

2001

J. Faist, M. Beck, T. Aellen, and E. Gini, "Quantum-cascade lasers based on bound-to-continuum transition," Appl. Phys. Lett. 78, 147-149 (2001).
[CrossRef]

K. B. Mogensen, N. J. Petersen, J. Hübner, and J. P. Kutter, "Monolithic integration of optical waveguides for absorbance detection in microfabricated electrophoresis devices," Electrophoresis 22, 3930-3938 (2001).
[CrossRef] [PubMed]

2000

B. Lendl, J. Frank, R. Schindler, A. Müller, M. Beck, and J. Faist, "Mid-infrared quantum cascade lasers for flow injection analysis," Anal. Chem. 72, 1645 (2000).
[CrossRef] [PubMed]

1999

V. M. Baev, T. Latz, and P. E. Toschek, "Laser intracavity absorption spectroscopy," Appl. Phys. B 69, 171-202 (1999).
[CrossRef]

1992

E. Verpoorte, A. Manz, H. Lüdi, A.E. Bruno, F. Maystre, B. Krattiger, H. M. Widmer, B.H. van der Schoot, and N.F. de Rooij, "A silicon flow cell for optical detection in miniaturized total chemical analysis systems," Sens. Actuators B 6, 66-70 (1992).
[CrossRef]

Anal. Chem.

C. Charlton, A. Katzir, and B. Mizaikoff, "Infrared evanescent field sensing with quantum cascade lasers and planar silver halide waveguides," Anal. Chem. 77, 4398-4403 (2005).
[CrossRef] [PubMed]

C. Charlton, M. Giovannini, J. Faist, B. Mizaikoff, "Fabrication and characterization of molecular beam epitaxy grown thin-film GaAs waveguides for mid-infrared evanescent field chemical sensing," Anal. Chem. 78, 4224-4227 (2006).
[CrossRef] [PubMed]

B. Lendl, J. Frank, R. Schindler, A. Müller, M. Beck, and J. Faist, "Mid-infrared quantum cascade lasers for flow injection analysis," Anal. Chem. 72, 1645 (2000).
[CrossRef] [PubMed]

Anal. Chim. Acta

D. Erickson and D. Li, "Integrated microfluidic devices," Anal. Chim. Acta 507, 11-26 (2004).
[CrossRef]

Appl. Phys. B

S. Schaden, A. Domínguez-Vidal, and B. Lendl, "Quantum cascade laser modulation for correction of matrix-induced background changes in aqueous samples," Appl. Phys. B 86, 347-351 (2007).
[CrossRef]

V. M. Baev, T. Latz, and P. E. Toschek, "Laser intracavity absorption spectroscopy," Appl. Phys. B 69, 171-202 (1999).
[CrossRef]

Appl. Phys. Lett

J. C. Galas, C. Peroz, Q. Kou, and Y. Chen, "Microfluidic dye laser intracavity absorption," Appl. Phys. Lett 89, 224101 (2006).
[CrossRef]

Appl. Phys. Lett.

J. Faist, M. Beck, T. Aellen, and E. Gini, "Quantum-cascade lasers based on bound-to-continuum transition," Appl. Phys. Lett. 78, 147-149 (2001).
[CrossRef]

R. Maulini, M. Beck, J. Faist, and E. Gini, "Broadband tuning of external cavity bound-to-continuum quantum-cascade lasers," Appl. Phys. Lett. 84, 1659-1661 (2004).
[CrossRef]

L. Diehl, D. Bour, S. Corzine, J. Zhu, G. Hofler, M. Loncar, M. Troccoli, and F. Capasso, "High-power quantum cascade lasers grown by low-pressure metal organic vapor-phase epitaxy operating in continuous wave above 400 K," Appl. Phys. Lett. 88, 201115 (2006).
[CrossRef]

Electron. Lett.

J. Z. Chen, Z. Liu, Y. S. Rumala, D. L. Sivco, and C. F. Gmachl, "Direct liquid cooling of room-temperature operated quantum cascade lasers," Electron. Lett. 42, 534-535 (2006).
[CrossRef]

Electrophoresis

K. B. Mogensen, N. J. Petersen, J. Hübner, and J. P. Kutter, "Monolithic integration of optical waveguides for absorbance detection in microfabricated electrophoresis devices," Electrophoresis 22, 3930-3938 (2001).
[CrossRef] [PubMed]

IEE Proc.: Optoelectron.

C. Charlton, F. de Melas, A. Inberg, N. Croitoru, and B. Mizaikoff, "Hollow-waveguide gas sensing with room-temperature quantum cascade lasers, "IEE Proc.: Optoelectron. 150, 306-309 (2003)
[CrossRef]

IEEE J. Quantum Electron.

A. Kosterev and F. Tittel, "Chemical sensors based on quantum cascade lasers," IEEE J. Quantum Electron. 38, 582-591 (2002).
[CrossRef]

Lab Chip

E. Verpoorte, "Chip vision - optics for microchips," Lab Chip 3, 42N-52N (2003).

Nat. Photonics.

C. Monat, P. Domachuk, and B. J. Eggleton, "Integrated optofluidics: a new river of light," Nat. Photonics. 1, 106-114 (2007).
[CrossRef]

Nature

D. Psaltis, S. R. Quake, and C. Yang, "Developing optofluidic technology through the fusion of microfluidics and optics," Nature 442, 381-386 (2006).
[CrossRef] [PubMed]

Opt. Express

Phys. Today

F. Capasso, C. Gmachl, D. L. Sivco, and A. Y. Cho, "Quantum cascade lasers," Phys. Today 55, 34-40 (2002).
[CrossRef]

Science

M. Beck, D. Hofstetter, T. Aellen, J. Faist, U. Oesterle, M. Ilegems, E. Gini, H. Melchior "Continuous wave operation of a mid-infrared semiconductor laser at room temperature," Science 295, 301-305 (2002).
[CrossRef] [PubMed]

Sens. Actuators B

E. Verpoorte, A. Manz, H. Lüdi, A.E. Bruno, F. Maystre, B. Krattiger, H. M. Widmer, B.H. van der Schoot, and N.F. de Rooij, "A silicon flow cell for optical detection in miniaturized total chemical analysis systems," Sens. Actuators B 6, 66-70 (1992).
[CrossRef]

Other

D. Lin-Vien, N. B. Colthup, W. G. Fateley, and J. G. Grasselli, The Handbook of Infrared and Raman Characteristic Frequencies of Organic Molecules (Academic Press, Boston, MA 1991).

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Figures (7)

Fig. 1.
Fig. 1.

(a) Simulated electric field distribution for a TM00 mode in a deep-etched 2- µm-wide ridge quantum cascade laser with a gold electrical contact on top, surrounded by a liquid. The laser active region is shown in red. (b) Dependence of the TM00 laser mode losses on liquid absorbance for deep-etched ridge waveguide quantum cascade lasers with various ridge widths. Also listed is the percentage of modal overlap with the liquid (in intensity) for ridges of various widths. Liquid refractive index, Re(n), is assumed to be 1.3 in the simulations. Simulations were performed using commercial software packages, BeamPROP (R-Soft Design Group, Inc) and COMSOL Multiphysics (COMSOL, Inc).

Fig. 2.
Fig. 2.

(a) Schematics of a narrow-ridge quantum cascade laser for inracavity absorption spectroscopy. (b,c) Scanning electron microscope images of the processed devices: (b) the cleaved edge of a laser ridge and (c) several narrow-ridge quantum cascade lasers processed on the same substrate.

Fig. 3.
Fig. 3.

(a)–(d) Different steps in fabrication of a microfluidic chamber; (e) devices after encapsulation; (f) a photograph of encapsulated devices.

Fig. 4.
Fig. 4.

(a) Current versus voltage (right axis) and light output versus current (left axis) characteristics obtained at 297K in pulsed mode (20ns pulses at 80kHz) with a 5-µm-wide 2.5-mm-long ridge encapsulated device with and without liquids. The threshold currents are ≈424±1.5 mA for device immersed in acetone, ≈435±1.5 mA for a devices immersed in water, ≈458±1.5 mA for a device immersed in isopropanol, and ≈457±1.5 mA for a device without liquids. (b) Emission spectra of the same device immersed in various liquids.

Fig. 5.
Fig. 5.

(a) Absorption spectra of liquids used in the experiments. (b) Emission spectra of an encapsulated 5-µm-wide, 2.5-mm-long ridge device immersed in various mixtures of isopropanol and acetone.

Fig. 6.
Fig. 6.

(a) Emission spectra of a 5-µm-wide 2.5-mm-long ridge encapsulated device with and without liquids. The spectra were obtained at 297 K. The device was driven with 540 mA current pulses, 20-ns-long at the repetition rate of 80 kHz. Note that the data in Figs. 4 and 6 is obtained with a different device. Inset shows the zoom-in of the laser modes situated around 1143 cm-1 (b) Dependence of the TM00 laser mode effective refractive index on a liquid refractive index for deep-etched ridge waveguide quantum cascade lasers with various ridge widths. The liquid absorbance, In(n), is assumed to be 0 in the simulations. Simulations were performed using commercial software packages, BeamPROP (R-Soft Design Group, Inc). Note that the dependence of the effective refractive index of the laser mode on the liquid refractive index may be used for microfluidic tuning of quantum cascade lasers [16].

Fig. 7.
Fig. 7.

Emission power from a 5-µm-wide 2.5-mm-long ridge encapsulated device immersed in (a) acetone (shaded areas) and a 1% volume solution of isopropanol in acetone (clear areas) and (b) methanol (shaded areas) and 5% volume solution of isopropanol in methanol (clear areas). The laser was operated in pulsed mode with 9 ns pulses at 80 kHz repetition rate. The peak current was kept fixed slightly above the lasing threshold.

Equations (1)

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L eff = ln ( I I 0 ) α ,

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