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DFB laser diodes in the wavelength range from 760 nm to 2.5 μm
Spectrochimica Acta Part A 60 (2004) 3243–3247
DFB laser diodes in the wavelength range from 760 nm to 2.5 m J. Seufert a,∗ , M. Fischer a , M. Legge a , J. Koeth a , R. Werner a , M. Kamp b , A. Forchel b a
nanoplus Nanosystems and Technologies GmbH, Oberer Kirschberg 4, D-97218 Gerbrunn, Germany b Technische Physik, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany Received 16 October 2003; accepted 12 November 2003
Abstract We present a novel device technology to produce DFB laser diodes which are suitable for tunable diode laser spectroscopy. The new technological approach employs lateral metal distributed feedback (DFB) gratings in close proximity to the laser ridge which results in single mode emission with high spectral purity and output powers as required for most spectroscopic applications. Over the entire wavelength range from the visible (760 nm) up to the near-infrared (2.5 m) single mode emission can be obtained for devices based on different semiconductor systems such as GaAs, InP and GaSb. Typical side mode suppression ratios are better than 35 dB for cw-room temperature operation and narrow linewidths ensure high spectroscopic resolution. © 2004 Elsevier B.V. All rights reserved. Keywords: DFB laser; Tunable diode laser spectroscopy
1. Introduction Tunable laser diode spectroscopy (TDLS) has become a field of active reserach during the last decade. Simultaneously, the number of commercial applications has steadily increased. A wide variety of gas species can be detected at levels in the ppm or even ppb range [1–7]. Industrial applications range from combustion diagnostics, detection of leaks, e.g. in gas carrying pipelines, environmental monitoring, up to medical applications [8–10] (e.g. blood glucose level sensors). The key component of modern TDLS applications are distributed feedback (DFB) laser diodes with narrow linewidths of the order of 10 MHz, wide tuning ranges and high side mode supression ratios to ensure high spectroscopic selectivity. These semiconductor laser diodes have widely replaced bulky and expensive dye lasers, which suffer, e.g. from fast degradation and insufficient wavelength stability. For different spectroscopic techniques such as, e.g. CARS or laser-induced flourescence, a high wavelength stability is required combined with a minaturized experimental setup, in particular for mobile use. ∗ Corresponding author. Tel.: +49-931-9082714; fax: +49-931-9082719. E-mail address: [email protected] (J. Seufert).
1386-1425/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2003.11.043
In this paper, we give some examples which illustrate that a novel approach based on metal gratings patterned laterally to a laser ridge enables the fabrication of DFB laser devices in the wavelength range from 760 to 2.5 m, which exceed the requirements of current and emerging TDLS applications. First we will introduce the technological concept of laterally coupled DFB laser which offers major advantages over conventional fabrication schemes in terms of yield, reliability and technological effort. In the second section of the paper, typical operation characteristics of these devices as well as the spectroscopically relevant current and temperature tuning capabilities for TDLS applications are demonstrated.
2. Experimental There are several concepts to establish distributed feedback within a laser cavity in order to tune the laser emission to a certain wavelength. The most commonly used approach is to etch a grating structure into either the laser waveguide or the active layer, which is then overgrown with different semiconductor material to form the upper structure of the laser. The grating will then provide a periodically varying index of refraction (index coupled laser) and/or a periodic modulation of the gain (complex or gain coupled laser)
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J. Seufert et al. / Spectrochimica Acta Part A 60 (2004) 3243–3247
within the laser structure. For pure index coupling the spectral position of the laser emission depends on the phase of the grating at the laser facet, which is random due to lack of sufficient positional control in the cleaving process. Therefore, the probabilty for single mode emission at the desired wavelength is low [11]. In addition, these lasers are sensitive to back reflection into the laser facet and usually an optical isolator is needed to prevent backscattered light from disturbing the laser mode. For complex- or gain-coupled lasers it has been shown that the sensitivity to backreflections is reduced, hence stable operation without optical isolators is possible [12,13]. Furthermore, a higher single mode yield as compared to index coupled DFB lasers has been demonstrated [14–16]. However, one major disadvantage of the conventional technology is the need for overgrowth for entirely semiconductor based index- and gain-coupled lasers, which inherently reduces the yield due to incorporation of overgrowth defects (especially, for oxygen sensitive Al-containing structures) into the laser structure. Our approach is based on a metal grating with grating period Λ which is defined by electron beam lithography in close proximity to the active region of the laser diode (see Fig. 1). The evanescent part of the light propagating along the ridge overlaps with this metal grating and Bragg diffraction leads to laser emission of wavelength λ = 2nΛ, where n is the effective refractive index of the structure and Λ the period of the grating structure. The use of a metal grating provides variations of the real and imaginary part of the refractive index with sufficient interaction strength with the evanescent tails of the laser mode in order to provide strong distributed feedback. The whole structure is then covered
with polymide and planarized. Finally, p- and n-contacts are processed. Due to the material independence of this technological approach, it is possible to provide single mode diode lasers in virtually all compound semiconductors systems based on InP, GaAs [17–19] and GaSb [20] which allows to cover a broad wavelength range from the red visible to the near-infrared region of the spectrum for TDLS applications. Fig. 2 illustrates the wavelength range which is covered by metal grating based complex-coupled DFB laser diodes together with the major absorption lines of some prominent species that can be detected via optical absorption. Some representative emission spectra of various DFB laser diodes are shown in the inset. The single mode output power is typically larger than 2 mW. Current spectroscopic analysis techniques based on tunable diode lasers rely on a sufficient tunability of the DFB laser emission wavelength either by temperature or by current. A number of groups have shown that by tuning the emission of DFB diode lasers over molecular absorption bands a precise measurement of the gas species concentration is possible. For example, the wavelength range around 2.0 m is suitable for CO2 , H2 O, NH3 or N2 O detection [21–24]. Fig. 3 demonstrates an example for the tuning characteristics of a 2004 nm DFB diode laser based on lateral metal gratings. Over the entire temperature range from 17 to 45 ◦ C single mode emission is achieved with a side mode suppression ratio of more than 30 dB covering a wavelength range of as wide as 6 nm. The tuning rate is in this case 0.19 nm ◦ C−1 . This “course” tuning mode by temperature may be used to shift the laser wavelength close to the gas
Fig. 1. Scanning electron micrograph of a complex coupled DFB laser diode showing the lateral metal Bragg grating.
J. Seufert et al. / Spectrochimica Acta Part A 60 (2004) 3243–3247
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Fig. 2. Wavelength range which can be covered with metal grating DFB laser diodes. Some representative DFB laser spectra are shown in the inset.
line to be monitored (in this case, CO2 ). It is interesting to note that the wavelength shift of a (multimode) reference laser without the Bragg grating is by a factor of approximately six higher. This is due to the fact that for the reference laser the spectral position of the modal gain and therefore, the emission wavelength shifts according to the variation of the semiconductor energy gap strongly with temperature, while for the complex coupled DFB lasers the temperature dependent wavelength shift is determined by the weak temperature dependence of the effective refractive index.
To scan the gas absorption line itself, the wavelength is usually varied by changing the drive current. As can be seen in Fig. 4, this measurement mode provides a significantly finer wavelength tuning rate of 0.025 nm mA−1 , which allows for sampling of narrow molecular absorption lines with excellent spectroscopic resolution. To ensure high spectroscopic selectivity, the laser emission linewidth must be far below the linewidth of the rotational transition of the specific molecule to be monitored. For example, typical linewidths of transitions within the ν1 + 2ν20 + ν3 band of CO2 around 2.0 m wavelength in air at room temperature conditions
Fig. 3. Spectra of a metal grating DFB laser diode at different heat sink temperatures. The wavelength tuning rate amounts to 0.19 nm ◦ C−1 .
Fig. 4. Wavelength tuning of a metal grating DFB laser diode by current variation.
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J. Seufert et al. / Spectrochimica Acta Part A 60 (2004) 3243–3247
rate to the lifetime criterion we can estimate a device lifetime of about 60 000 h. In summary, we have presented data on complex coupled metal grating based DFB laser diodes which show that these devices are promising coherent single mode light sources for tunable diode laser spectroscopy and for a wide variety of sensing applications.
References
Fig. 5. Homodynesignal of the emission line of a complex coupled DFB laser emitting at a wavelength of about 1.5 m.
Fig. 6. Threshold current of a GaSb based DFB-laser (wavelength 2.004 m) for a test period of 15 000 h.
and atmospheric pressure are approximately 5 GHz [21,25]. Fig. 5 shows that the emission linewidth of a complex coupled DFB laser as measured with a homodyne high frequency setup.1 The single mode laser linewidth is far beyond the transition linewidth and amounts to about 15 MHz. For commercial applications of these lasers a long device lifetime and stable emission over the lifetime is required. The lifetime is defined as the length of time the device can run at constant power until the power is reduced by 20% (standard ISO/FDIS 17526). An overview over current standards for calibrating lifetime tests can be found in [26]. In Fig. 6, the threshold current for a typical DFB laser in the 2.0 m wavelength range is depicted during a test period of more than 15 000 h. The laser was mounted on a standard TO 9.0 mm header and operated at constant current and room temperature. Within this time interval the threshold current increases only slightly by about 5%. By extrapolating this 1 We wish to note here that the maximum wavelength limit of the setup is 1.75 m. Therefore, this measurement was taken with a complex coupled DFB laser emitting at about 1.5 m wavelength.
[1] H.I. Schiff, G.I. Mackay, J. Bechara, The use of tunable diodelaser absorption spectroscopy for atmospheric measurements, in: M.W. Sigrist (Ed.), Air Monitoring by Spectroscopic Techniques, Chemical Analysis Series, vol. 127, Wiley, New York, 1994. [2] D.J. Brassington, Tunable diode-laser absorption spectroscopy for the measurement of atmospheric species, in: R.E. Hester, R.J. Clark (Eds.), Spectroscopy in Environmental Science, Advances in Spectroscopy, vol. 24, Wiley, Chichester, 1994, pp. 85–148. [3] P. Werle, Diode-laser sensors for in-situ gas analysis, in: P. Hering, J.P. Lay, S. Stry (Eds.), Lasers in Environmental and Life Sciences—Modern Analytical Methods, Springer, Heidelberg, 2004, pp. 223–243. [4] R.F. Curl, F.K. Tittel, Tunable infrared laser spectroscopy, Ann. Rep. Prog. Chem. C 98 (2002) 217–270. [5] M.S. Zahniser, D.D. Nelson, C.E. Kolb, Tunable infrared laser differential absorption spectroscopy (TILDAS) sensors for combustion exhaust pollutant quantification, in: K. Kohse-Hoinghaus, J.B. Jeffries (Eds.), Applied Combustion Diagnostics, Taylor & Francis, New York, 2002, p. 648. [6] P. Werle, A review of recent advances in semiconductor laser-based gas monitors, Spectrochim. Acta A54 (1998) 197–236. [7] C.R. Webster, R.T. Menzies, E.D. Hinkley, Infrared laser absorption: theory and applications, in: R.M. Measures (Ed.), Laser Remote Chemical Analysis—Chemical Analysis Series, vol. 94, Wiley, New York, 1988, pp. 163–532. [8] J.Y. Qu, L. Shao, Rev. Sci. Instrum. 72 (2001) 101. [9] A.J. Berger, T.W. Koo, I. Itzkan, et al., Appl. Opt. 38 (1999) 2916. [10] E. Pringsheim, E. Terpetschnig, S.A. Piletsky, et al., Adv. Mater. 11 (1999) 865. [11] J. Buus, Electron. Lett. 21 (1985) 179. [12] Z.M. Chuang, C.Y. Wang, W. Lin, H.H. Liao, J.Y. Su, Y.K. Tu, IEEE Photonics Technol. Lett. 8 (1997) 1438. [13] H. Lu, T. Makino, G.P. Li, IEEE J. Quantum Electron. 31 (1995) 1443. [14] K. David, G. Morthier, P. Vankwikelberge, R.G. Baets, T. Wolf, B. Borchert, IEEE J. Quantum Electron. 27 (1991) 1714. [15] C. Park, J.S. Kim, D.K. Oh, D.H. Jang, C.Y. Park, J.H. Ahn, H.M. Kim, H.R. Choo, H. Kim, K.E. Pyun, IEEE Photonics Technol. Lett. 9 (1997) 22. [16] G.P. Li, T. Makino, R. Moore, N. Puetz, K.-W. Leong, H. Lu, IEEE J. Quantum Electron. 29 (1993) 1736. [17] M. Kamp, J. Hofmann, F. Schäfer, M. Reinhardt, M. Fischer, T. Bleuel, J.P. Reithmaier, A. Forchel, Opt. Mater. (Amsterdam) 17 (2001) 19. [18] M. Kamp, J. Hofmann, A. Forchel, F. Schäfer, J.P. Reithmaier, Appl. Phys. Lett. 74 (1999) 483. [19] D. Gollub, M. Fischer, M. Kamp, A. Forchel, Appl. Phys. Lett. 81 (2002) 4330. [20] T. Bleuel, M. Brockhaus, J. Koeth, J. Hofmann, R. Werner, A. Forchel, Proc. SPIE Int. Soc. Opt. Eng. 3858 (1999) 119. [21] R.M. Mihalcea, M.E. Webber, D.S. Baer, R.K. Hanson, G.S. Feller, W.B. Chapman, Appl. Phys. B67 (1998) 288.
J. Seufert et al. / Spectrochimica Acta Part A 60 (2004) 3243–3247 [22] A. Vicet, D.A. Yarekha, A. Ouvrard, R. Teissier, C. Alibert, A.N. Baranov, IEE P-Optoelectron. 150 (2003) 310. [23] Y. Rouillard, F. Genty, A. Perona, A. Vicet, D.A. Yarekha, G. Boissier, P. Greech, A.N. Baranov, C. Alibert, Philos. Trans. R. Soc. A 359 (2001) 581.
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[24] A. Vicet, J.C. Nicolas, F. Genty, Y. Rouillard, E.M. Skouri, A.N. Baranov, C. Alibert, IEE P-Optoelectron. 147 (2000) 172. [25] HITRAN96 database, www.hitran.com. [26] Photonics Spectra, July 2003, Laurin Publishing Co. Inc., Pittsfield, MA, USA.
DFB laser diodes in the wavelength range from 760 nm to 2.5 m J. Seufert a,∗ , M. Fischer a , M. Legge a , J. Koeth a , R. Werner a , M. Kamp b , A. Forchel b a
nanoplus Nanosystems and Technologies GmbH, Oberer Kirschberg 4, D-97218 Gerbrunn, Germany b Technische Physik, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany Received 16 October 2003; accepted 12 November 2003
Abstract We present a novel device technology to produce DFB laser diodes which are suitable for tunable diode laser spectroscopy. The new technological approach employs lateral metal distributed feedback (DFB) gratings in close proximity to the laser ridge which results in single mode emission with high spectral purity and output powers as required for most spectroscopic applications. Over the entire wavelength range from the visible (760 nm) up to the near-infrared (2.5 m) single mode emission can be obtained for devices based on different semiconductor systems such as GaAs, InP and GaSb. Typical side mode suppression ratios are better than 35 dB for cw-room temperature operation and narrow linewidths ensure high spectroscopic resolution. © 2004 Elsevier B.V. All rights reserved. Keywords: DFB laser; Tunable diode laser spectroscopy
1. Introduction Tunable laser diode spectroscopy (TDLS) has become a field of active reserach during the last decade. Simultaneously, the number of commercial applications has steadily increased. A wide variety of gas species can be detected at levels in the ppm or even ppb range [1–7]. Industrial applications range from combustion diagnostics, detection of leaks, e.g. in gas carrying pipelines, environmental monitoring, up to medical applications [8–10] (e.g. blood glucose level sensors). The key component of modern TDLS applications are distributed feedback (DFB) laser diodes with narrow linewidths of the order of 10 MHz, wide tuning ranges and high side mode supression ratios to ensure high spectroscopic selectivity. These semiconductor laser diodes have widely replaced bulky and expensive dye lasers, which suffer, e.g. from fast degradation and insufficient wavelength stability. For different spectroscopic techniques such as, e.g. CARS or laser-induced flourescence, a high wavelength stability is required combined with a minaturized experimental setup, in particular for mobile use. ∗ Corresponding author. Tel.: +49-931-9082714; fax: +49-931-9082719. E-mail address: [email protected] (J. Seufert).
1386-1425/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2003.11.043
In this paper, we give some examples which illustrate that a novel approach based on metal gratings patterned laterally to a laser ridge enables the fabrication of DFB laser devices in the wavelength range from 760 to 2.5 m, which exceed the requirements of current and emerging TDLS applications. First we will introduce the technological concept of laterally coupled DFB laser which offers major advantages over conventional fabrication schemes in terms of yield, reliability and technological effort. In the second section of the paper, typical operation characteristics of these devices as well as the spectroscopically relevant current and temperature tuning capabilities for TDLS applications are demonstrated.
2. Experimental There are several concepts to establish distributed feedback within a laser cavity in order to tune the laser emission to a certain wavelength. The most commonly used approach is to etch a grating structure into either the laser waveguide or the active layer, which is then overgrown with different semiconductor material to form the upper structure of the laser. The grating will then provide a periodically varying index of refraction (index coupled laser) and/or a periodic modulation of the gain (complex or gain coupled laser)
3244
J. Seufert et al. / Spectrochimica Acta Part A 60 (2004) 3243–3247
within the laser structure. For pure index coupling the spectral position of the laser emission depends on the phase of the grating at the laser facet, which is random due to lack of sufficient positional control in the cleaving process. Therefore, the probabilty for single mode emission at the desired wavelength is low [11]. In addition, these lasers are sensitive to back reflection into the laser facet and usually an optical isolator is needed to prevent backscattered light from disturbing the laser mode. For complex- or gain-coupled lasers it has been shown that the sensitivity to backreflections is reduced, hence stable operation without optical isolators is possible [12,13]. Furthermore, a higher single mode yield as compared to index coupled DFB lasers has been demonstrated [14–16]. However, one major disadvantage of the conventional technology is the need for overgrowth for entirely semiconductor based index- and gain-coupled lasers, which inherently reduces the yield due to incorporation of overgrowth defects (especially, for oxygen sensitive Al-containing structures) into the laser structure. Our approach is based on a metal grating with grating period Λ which is defined by electron beam lithography in close proximity to the active region of the laser diode (see Fig. 1). The evanescent part of the light propagating along the ridge overlaps with this metal grating and Bragg diffraction leads to laser emission of wavelength λ = 2nΛ, where n is the effective refractive index of the structure and Λ the period of the grating structure. The use of a metal grating provides variations of the real and imaginary part of the refractive index with sufficient interaction strength with the evanescent tails of the laser mode in order to provide strong distributed feedback. The whole structure is then covered
with polymide and planarized. Finally, p- and n-contacts are processed. Due to the material independence of this technological approach, it is possible to provide single mode diode lasers in virtually all compound semiconductors systems based on InP, GaAs [17–19] and GaSb [20] which allows to cover a broad wavelength range from the red visible to the near-infrared region of the spectrum for TDLS applications. Fig. 2 illustrates the wavelength range which is covered by metal grating based complex-coupled DFB laser diodes together with the major absorption lines of some prominent species that can be detected via optical absorption. Some representative emission spectra of various DFB laser diodes are shown in the inset. The single mode output power is typically larger than 2 mW. Current spectroscopic analysis techniques based on tunable diode lasers rely on a sufficient tunability of the DFB laser emission wavelength either by temperature or by current. A number of groups have shown that by tuning the emission of DFB diode lasers over molecular absorption bands a precise measurement of the gas species concentration is possible. For example, the wavelength range around 2.0 m is suitable for CO2 , H2 O, NH3 or N2 O detection [21–24]. Fig. 3 demonstrates an example for the tuning characteristics of a 2004 nm DFB diode laser based on lateral metal gratings. Over the entire temperature range from 17 to 45 ◦ C single mode emission is achieved with a side mode suppression ratio of more than 30 dB covering a wavelength range of as wide as 6 nm. The tuning rate is in this case 0.19 nm ◦ C−1 . This “course” tuning mode by temperature may be used to shift the laser wavelength close to the gas
Fig. 1. Scanning electron micrograph of a complex coupled DFB laser diode showing the lateral metal Bragg grating.
J. Seufert et al. / Spectrochimica Acta Part A 60 (2004) 3243–3247
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Fig. 2. Wavelength range which can be covered with metal grating DFB laser diodes. Some representative DFB laser spectra are shown in the inset.
line to be monitored (in this case, CO2 ). It is interesting to note that the wavelength shift of a (multimode) reference laser without the Bragg grating is by a factor of approximately six higher. This is due to the fact that for the reference laser the spectral position of the modal gain and therefore, the emission wavelength shifts according to the variation of the semiconductor energy gap strongly with temperature, while for the complex coupled DFB lasers the temperature dependent wavelength shift is determined by the weak temperature dependence of the effective refractive index.
To scan the gas absorption line itself, the wavelength is usually varied by changing the drive current. As can be seen in Fig. 4, this measurement mode provides a significantly finer wavelength tuning rate of 0.025 nm mA−1 , which allows for sampling of narrow molecular absorption lines with excellent spectroscopic resolution. To ensure high spectroscopic selectivity, the laser emission linewidth must be far below the linewidth of the rotational transition of the specific molecule to be monitored. For example, typical linewidths of transitions within the ν1 + 2ν20 + ν3 band of CO2 around 2.0 m wavelength in air at room temperature conditions
Fig. 3. Spectra of a metal grating DFB laser diode at different heat sink temperatures. The wavelength tuning rate amounts to 0.19 nm ◦ C−1 .
Fig. 4. Wavelength tuning of a metal grating DFB laser diode by current variation.
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J. Seufert et al. / Spectrochimica Acta Part A 60 (2004) 3243–3247
rate to the lifetime criterion we can estimate a device lifetime of about 60 000 h. In summary, we have presented data on complex coupled metal grating based DFB laser diodes which show that these devices are promising coherent single mode light sources for tunable diode laser spectroscopy and for a wide variety of sensing applications.
References
Fig. 5. Homodynesignal of the emission line of a complex coupled DFB laser emitting at a wavelength of about 1.5 m.
Fig. 6. Threshold current of a GaSb based DFB-laser (wavelength 2.004 m) for a test period of 15 000 h.
and atmospheric pressure are approximately 5 GHz [21,25]. Fig. 5 shows that the emission linewidth of a complex coupled DFB laser as measured with a homodyne high frequency setup.1 The single mode laser linewidth is far beyond the transition linewidth and amounts to about 15 MHz. For commercial applications of these lasers a long device lifetime and stable emission over the lifetime is required. The lifetime is defined as the length of time the device can run at constant power until the power is reduced by 20% (standard ISO/FDIS 17526). An overview over current standards for calibrating lifetime tests can be found in [26]. In Fig. 6, the threshold current for a typical DFB laser in the 2.0 m wavelength range is depicted during a test period of more than 15 000 h. The laser was mounted on a standard TO 9.0 mm header and operated at constant current and room temperature. Within this time interval the threshold current increases only slightly by about 5%. By extrapolating this 1 We wish to note here that the maximum wavelength limit of the setup is 1.75 m. Therefore, this measurement was taken with a complex coupled DFB laser emitting at about 1.5 m wavelength.
[1] H.I. Schiff, G.I. Mackay, J. Bechara, The use of tunable diodelaser absorption spectroscopy for atmospheric measurements, in: M.W. Sigrist (Ed.), Air Monitoring by Spectroscopic Techniques, Chemical Analysis Series, vol. 127, Wiley, New York, 1994. [2] D.J. Brassington, Tunable diode-laser absorption spectroscopy for the measurement of atmospheric species, in: R.E. Hester, R.J. Clark (Eds.), Spectroscopy in Environmental Science, Advances in Spectroscopy, vol. 24, Wiley, Chichester, 1994, pp. 85–148. [3] P. Werle, Diode-laser sensors for in-situ gas analysis, in: P. Hering, J.P. Lay, S. Stry (Eds.), Lasers in Environmental and Life Sciences—Modern Analytical Methods, Springer, Heidelberg, 2004, pp. 223–243. [4] R.F. Curl, F.K. Tittel, Tunable infrared laser spectroscopy, Ann. Rep. Prog. Chem. C 98 (2002) 217–270. [5] M.S. Zahniser, D.D. Nelson, C.E. Kolb, Tunable infrared laser differential absorption spectroscopy (TILDAS) sensors for combustion exhaust pollutant quantification, in: K. Kohse-Hoinghaus, J.B. Jeffries (Eds.), Applied Combustion Diagnostics, Taylor & Francis, New York, 2002, p. 648. [6] P. Werle, A review of recent advances in semiconductor laser-based gas monitors, Spectrochim. Acta A54 (1998) 197–236. [7] C.R. Webster, R.T. Menzies, E.D. Hinkley, Infrared laser absorption: theory and applications, in: R.M. Measures (Ed.), Laser Remote Chemical Analysis—Chemical Analysis Series, vol. 94, Wiley, New York, 1988, pp. 163–532. [8] J.Y. Qu, L. Shao, Rev. Sci. Instrum. 72 (2001) 101. [9] A.J. Berger, T.W. Koo, I. Itzkan, et al., Appl. Opt. 38 (1999) 2916. [10] E. Pringsheim, E. Terpetschnig, S.A. Piletsky, et al., Adv. Mater. 11 (1999) 865. [11] J. Buus, Electron. Lett. 21 (1985) 179. [12] Z.M. Chuang, C.Y. Wang, W. Lin, H.H. Liao, J.Y. Su, Y.K. Tu, IEEE Photonics Technol. Lett. 8 (1997) 1438. [13] H. Lu, T. Makino, G.P. Li, IEEE J. Quantum Electron. 31 (1995) 1443. [14] K. David, G. Morthier, P. Vankwikelberge, R.G. Baets, T. Wolf, B. Borchert, IEEE J. Quantum Electron. 27 (1991) 1714. [15] C. Park, J.S. Kim, D.K. Oh, D.H. Jang, C.Y. Park, J.H. Ahn, H.M. Kim, H.R. Choo, H. Kim, K.E. Pyun, IEEE Photonics Technol. Lett. 9 (1997) 22. [16] G.P. Li, T. Makino, R. Moore, N. Puetz, K.-W. Leong, H. Lu, IEEE J. Quantum Electron. 29 (1993) 1736. [17] M. Kamp, J. Hofmann, F. Schäfer, M. Reinhardt, M. Fischer, T. Bleuel, J.P. Reithmaier, A. Forchel, Opt. Mater. (Amsterdam) 17 (2001) 19. [18] M. Kamp, J. Hofmann, A. Forchel, F. Schäfer, J.P. Reithmaier, Appl. Phys. Lett. 74 (1999) 483. [19] D. Gollub, M. Fischer, M. Kamp, A. Forchel, Appl. Phys. Lett. 81 (2002) 4330. [20] T. Bleuel, M. Brockhaus, J. Koeth, J. Hofmann, R. Werner, A. Forchel, Proc. SPIE Int. Soc. Opt. Eng. 3858 (1999) 119. [21] R.M. Mihalcea, M.E. Webber, D.S. Baer, R.K. Hanson, G.S. Feller, W.B. Chapman, Appl. Phys. B67 (1998) 288.
J. Seufert et al. / Spectrochimica Acta Part A 60 (2004) 3243–3247 [22] A. Vicet, D.A. Yarekha, A. Ouvrard, R. Teissier, C. Alibert, A.N. Baranov, IEE P-Optoelectron. 150 (2003) 310. [23] Y. Rouillard, F. Genty, A. Perona, A. Vicet, D.A. Yarekha, G. Boissier, P. Greech, A.N. Baranov, C. Alibert, Philos. Trans. R. Soc. A 359 (2001) 581.
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[24] A. Vicet, J.C. Nicolas, F. Genty, Y. Rouillard, E.M. Skouri, A.N. Baranov, C. Alibert, IEE P-Optoelectron. 147 (2000) 172. [25] HITRAN96 database, www.hitran.com. [26] Photonics Spectra, July 2003, Laurin Publishing Co. Inc., Pittsfield, MA, USA.