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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 4 — Feb. 25, 2013
  • pp: 4518–4530
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High-power arrays of quantum cascade laser master-oscillator power-amplifiers

Patrick Rauter, Stefan Menzel, Anish K. Goyal, Christine A. Wang, Antonio Sanchez, George Turner, and Federico Capasso  »View Author Affiliations


Optics Express, Vol. 21, Issue 4, pp. 4518-4530 (2013)
http://dx.doi.org/10.1364/OE.21.004518


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Abstract

We report on multi-wavelength arrays of master-oscillator power-amplifier quantum cascade lasers operating at wavelengths between 9.2 and 9.8 μm. All elements of the high-performance array feature longitudinal (spectral) as well as transverse single-mode emission at peak powers between 2.7 and 10 W at room temperature. The performance of two arrays that are based on different seed-section designs is thoroughly studied and compared. High output power and excellent beam quality render the arrays highly suitable for stand-off spectroscopy applications.

© 2013 OSA

1. Introduction

Recently, quantum cascade lasers (QCLs [1

1. J. Faist, F. Capasso, D. L. Sivco, C. Sirtori, A. L. Hutchinson, and A. Y. Cho, “Quantum cascade laser,” Science 264(5158), 553–556 (1994). [CrossRef] [PubMed]

,2

2. C. Gmachl, F. Capasso, D. L. Sivco, and A. Y. Cho, “Recent progress in quantum cascade lasers and applications,” Rep. Prog. Phys. 64(11), 1533–1601 (2001). [CrossRef]

], ) have seen increased use as sources for stand-off detection and spectroscopy systems in the mid-infrared [3

3. A. K. Goyal, M. Spencer, M. Kelly, J. Costa, M. DiLiberto, E. Meyer, and T. Jeys, “Active infrared multispectral imaging of chemicals on surfaces,” Proc. SPIE 8018, 80180N, 80180N-11 (2011). [CrossRef]

5

5. K. Degreif, S. Rademacher, P. Dasheva, F. Fuchs, S. Hugger, F. Schnürer, and W. Schweikert, “Stand-off explosive detection on surfaces using multispectral MIR-imaging,” Proc. SPIE 7945, 79450P, 79450P-8 (2011). [CrossRef]

]. The requirements for such systems have continued to motivate considerable research interest, aiming for the realization of single-mode high-power QCL sources with single-lobed intensity distributions in the far-field. Most of the recently demonstrated QCL-based spectroscopy systems rely on an external grating for the selection of the emission wavelength of a single external-cavity QCL [6

6. For a review on external cavity QCLs see:A. Hugi, R. Maulini, and J. Faist, “External cavity quantum cascade laser,” Semicond. Sci. Technol. 25(8), 083001 (2010). [CrossRef]

]. As an alternative that does not require mechanical means for tuning, arrays of single-mode QCL devices allow purely electronic addressing of different wavelengths [7

7. B. G. Lee, M. A. Belkin, C. Pflügl, L. Diehl, H. A. Zhang, R. M. Audet, J. MacArthur, D. P. Bour, S. W. Corzine, G. E. Höfler, and F. Capasso, “DFB quantum cascade laser arrays,” IEEE J. Quantum Electron. 45(5), 554–565 (2009). [CrossRef]

,8

8. E. Mujagic, C. Schwarzer, Y. Yao, J. Chen, C. Gmachl, and G. Strasser, “Two-dimensional broadband distributed-feedback quantum cascade laser arrays,” Appl. Phys. Lett. 98(14), 141101 (2011). [CrossRef]

]. Single-mode operation of each array element can be achieved using distributed feedback (DFB) gratings. Despite the recent demonstration of DFB QCLs with an excellent cw output power of 2.4 W [9

9. Q. Y. Lu, Y. Bai, N. Bandyopadhyay, S. Slivken, and M. Razeghi, “2.4 W room temperature continuous wave operation of distributed feedback quantum cascade lasers,” Appl. Phys. Lett. 98(18), 181106 (2011). [CrossRef]

], single-mode DFB QCLs as array elements have so far been limited in their peak output power. This is due to the upper limit in ridge width for lateral single-mode operation. A powerful way to increase the output power of a QCL device while maintaining good beam quality is the realization of master-oscillator power-amplifiers (MOPAs). The latter are formed by a DFB seed laser monolithically integrated with an optical amplifier [10

10. H. Zhang, A. Seetharaman, P. Johnson, G. Luo, and H. Q. Le, “High-gain low-noise mid-infrared quantum cascade optical preamplifier for receiver,” IEEE Photon. Technol. Lett. 17(1), 13–15 (2005). [CrossRef]

] and have been successfully implemented for both diode lasers [11

11. D. F. Welch, D. Mehuys, R. Parke, R. Waarts, D. Scifres, and W. Streifer, “Coherent operation of monolithically integrated master oscillator amplifiers,” Electron. Lett. 26(17), 1327–1329 (1990). [CrossRef]

,12

12. H. Wenzel, K. Paschke, O. Brox, F. Bugge, J. Fricke, A. Ginolas, A. Knauer, P. Ressel, and G. Erbert, “10W continuous-wave monolithically integrated master-oscillator power-amplifier,” Electron. Lett. 43(3), 160–161 (2007). [CrossRef]

] and QCLs [13

13. M. Troccoli, C. Gmachl, F. Capasso, D. L. Sivco, and A. Y. Cho, “Mid-infrared (λ~7.4µm) quantum cascade laser amplifier for high power single-mode emission and improved beam quality,” Appl. Phys. Lett. 80(22), 4103–4105 (2002). [CrossRef]

,14

14. S. Menzel, L. Diehl, C. Pflügl, A. Goyal, C. Wang, A. Sanchez, G. Turner, and F. Capasso, “Quantum cascade laser master-oscillator power-amplifier with 1.5 W output power at 300 K,” Opt. Express 19(17), 16229–16235 (2011). [CrossRef] [PubMed]

]. Very recently, the authors have demonstrated an array of MOPA QCLs operating at a series of wavelengths between 9.2 and 9.8 μm with single-mode peak powers between 0.8 and 3.9 W [15

15. P. Rauter, S. Menzel, A. K. Goyal, B. Gökden, C. A. Wang, A. Sanchez, G. Turner, and F. Capasso, “Master-oscillator power-amplifier quantum cascade laser array,” Appl. Phys. Lett. 101(26), 261117 (2012). [CrossRef]

]. In this work, we compare this first-generation MOPA array (called Array 1 in the following) to an array of MOPA QCLs featuring a DFB grating of a simplified design that will be called Array 2. A thorough experimental characterization of both arrays allows the comparison between the two design strategies, showing that a simple DFB grating approach proves superior to a counterpart based on a quarter-wave-shifted (QWS) DFB section in terms of single-mode output power. The MOPA array presented in this work (Array 2) features single-mode peak powers between 2.7 W and 10 W and excellent beam quality.

2. Material and fabrication

The material used for both Array 1 and Array 2 is a GaInAs/AlInAs broadband bound-to-continuum heterostructure [16

16. A. Wittmann, T. Gresch, E. Gini, L. Hvozdara, N. Hoyler, M. Giovannini, and J. Faist, “High-performance bound-to-continuum quantum-cascade laser for broad-gain applications,” IEEE J. Quantum Electron. 44(1), 36–40 (2008). [CrossRef]

] grown lattice-matched on a conducting InP substrate by organometallic vapor phase epitaxy (OMVPE). A 3.5-μm-thick, highly silicon-doped InP layer (n = 1 × 1017cm−3) is followed by a 0.52-μm-thick layer of GaInAs (n = 3 × 1016cm−3) and the active region composed of 35 periods of the following layer sequence (AlInAs barriers bold, GaInAs wells Roman, thickness in nm, underlined layers doped to n = 1.5 × 1017cm−3): 4.4/1.7/0.9/5.3/1.1/5.2/1.2/4.7/1.3/4.2/1.5/3.9/1.6/3.4/1.8/3.1/2.1/2.8/2.5/2.7/3.2/ 2.7/ 3.6/2.5. Following the growth of an additional injector sequence and 520 nm of GaInAs (n = 3 × 1016cm−3), the structure is completed by the upper waveguide cladding formed by3.5 μm of InP (n = 1 × 1017cm−3), the top contact layer composed of 0.5 μm of InP (n = 5 × 1018cm−3), and 20 nm of GaInAs (n = 1.8 × 1019cm−3).

An array of sixteen QCL MOPA devices was fabricated. Each MOPA comprises two sections, a narrow DFB ridge acting as a master-oscillator (MO), and a tapered power-amplifier (PA). While the geometric layout and dimensions of both arrays described in this work are identical to that in reference [15

15. P. Rauter, S. Menzel, A. K. Goyal, B. Gökden, C. A. Wang, A. Sanchez, G. Turner, and F. Capasso, “Master-oscillator power-amplifier quantum cascade laser array,” Appl. Phys. Lett. 101(26), 261117 (2012). [CrossRef]

], the two arrays differ in their DFB grating design. Array 2 features a conventional first-order Bragg grating, while a QWS was introduced in the grating of Array 1. To fabricate DFB gratings, the top InP cladding layer was first removed by wet etching in a HCl:H2O (1:1) solution. The grating was then defined by electron-beam lithography and subsequent ion-etching into the exposed 520-nm-thick GaInAs layer with an etch depth of 250 nm. The DFB grating period was varied between 1.55 μm (device 1) and 1.44 μm (device 16) in order to achieve a different emission wavelength for each array element. After the DFB gratings were etched, the InP cladding and top-contact layer sequence were regrown using OMVPE. The device geometry was defined by reactive ion-etching of double trenches where 13 μm wide DFB ridges and an amplifier tapering half-angle of 1.3° were realized. A Ti/Au metallization was applied as a ridge top contact and 450-nm-thick SiN provides electrical insulation.

The MO and PA sections were separated electrically by a 100-μm-wide gap in the gold metallization. The MO and PA sections were each 2-mm-long and the output facet was 110-μm-wide. Anti-reflection (AR) coatings were applied to the latter allowing for strong optical amplification in single-pass travelling-wave configuration. The AR coating is composed of 842-nm-thick ZnS (refractive index of 2.2) and 1280-nm-thick YF3 (refractive index of 1.415). Adhesion between the layers is provided by 30 nm of Y2O3. The substrate was maintained at 175°C during e-beam evaporation of the coating. During the deposition of YF3, argon ion-assisted-deposition was used to increase the density of the film and to improve its mechanical stability under thermal cycling. The AR coating applied to the front facet of the PA increased the self-lasing threshold of the tapered section from about 4.2 A to 6.6 A in the case of an unpumped MO. Figures 1(a)
Fig. 1 Layout and packaging. a) The elements of Array 2 comprise a 2-mm-long DFB section and an equally long tapered power-amplifier with a taper angle of 1.3°. b) Packaged array, allowing individual electronic addressing of both device sections for all of the array elements. c) Top view of three elements of Array 1, for which a quarter-wave shift was included in the DFB grating at the indicated position. Note that 360 μm of the 2-mm-long DFB section are left unpumped.
and 1(c) show a top view of three elements of Array 2 and Array 1, respectively. The top metallization of the PA is extended alongside the MO section of the devices in order to enable clean bonding and packaging. The array chip was mounted epilayer up on a heat sink and packaged as seen in Fig. 1(b).

3. Experimental results for array 2

Each element of Array 2 was characterized under pulsed operation (10 kHz repetition rate, 25 ns MO pulse length, 100 ns PA pulse length) at a heat sink temperature of 18°C. A short MO pulse was employed to limit spectral broadening due to self-heating of the device. The difference in the pulse lengths for the MO and PA is due to limitations of the pulse generator used for driving the PA. The length of the output radiation bursts is determined by the MO pulse length as the amplifier is driven below its self-lasing threshold. This gives a duty cycle of 0.025% for all of the experiments in this work except when explicitly mentioned otherwise.

A systematic characterization procedure determined the maximum achievable peak output power of each MOPA element while maintaining a side-mode suppression ratio (SMSR) of at least 20 dB. This was accomplished by monitoring the output spectra of the individual devices using a Fourier-transform infrared spectrometer while the currents through the MO and PA were successively increased.

Figure 3
Fig. 3 Optimum driving conditions: The plot presents the values for master-oscillator (blue bars) and power-amplifier peak currents (green bars), at which the spectra in Fig. 2 have been acquired, together with the corresponding peak power values (red bars).
presents the driving parameters at which the spectra shown in Fig. 2 were acquired along with the corresponding peak powers. The highest single-mode peak powers are reached by elements which allow simultaneous driving of the MO close to rollover (around 2 A) and of the PA close to its self-lasing threshold (devices 5, 8, 9, 10 and 12). Increasing the PA or MO current beyond the values in Fig. 3 leads to unwanted multi-mode behavior of the devices, where the absolute upper limit for driving the MO is given by the rollover current. Representative multimode spectra are shown in Fig. 4
Fig. 4 Additional modes at high driving currents. The plot shows three different scenarios compromising the single-mode operation of the array elements for driving current values in excess of those in Fig. 3. The spectra are normalized to the maximum intensity of the dominant DFB mode. a) An increase of the master-oscillator current of device 13 beyond 1.4 A results in lasing at both the high- and low-frequency DFB mode. b) For the same array element, an increase in the power-amplifier current beyond 5.2 A enables lasing at Fabry-Perot modes of the cavity formed by the MO and PA sections. Note that the additional modes are located at low frequencies and the DFB mode at 1077.5 cm−1 is not shown in the plot. c) When increasing the PA current of device 5 in excess of 6.2 A, Fabry-Perot modes (labeled 2 and 3) appear within the indicated photonic bandgap in addition to the high-frequency DFB mode (labeled 1).
for device 5 and device 13. For the latter, the highest output power for single-mode operation is achieved by driving the MO and PA at 1.4 A and 5.2 A, respectively. Both increasing the MO current to 1.6 A (Fig. 4(a)) and raising the PA current to 5.4 A (Fig. 4(b)) results in multi-mode behavior, where the origin of the additional modes is discussed in the following.

For all of the array elements, an increase of the PA current beyond the values given in Fig. 3 results in a degradation of the SMSR below 20 dB due to the appearance of a group of additional modes (with the exception of device 9, as discussed later on). These groups of additional modes can be identified as Fabry-Perot (FP) modes and typically appear at two different spectral positions. For devices 4, 11, 13, 14 and 15, the FP modes appear in the spectral region around 1010 cm−1 and exhibit a free spectral range of 0.37 cm−1 (see Fig. 4(b)), suggesting a cavity length of 4 mm which is equivalent to the total device length. The cavity for these modes is thus formed by the two device facets. Devices 2, 3, 5, 6, 7, 8, 10 and 12, on the other hand, exhibit lasing at additional modes that are in, and close to, the photonic bandgap with a free spectral range of 0.8 cm−1 (see Fig. 4(c)). These modes originate from self-lasing of the tapered PA section where the DFB section acts as a distributed Bragg reflector forming a 2-mm-long cavity together with the PA front facet. Figure 4(c) shows a representative spectrum for device 5 at high PA currents, where the PA exhibits self-lasing at FP modes within the photonic bandgap (labeled 2 and 3) in addition to the high-frequencyDFB mode (labeled 1) seeded by the MO. In future devices, higher single-mode power can be achieved by decreasing the residual reflectivity of the AR coated facet and thus further suppressing self-lasing of the PA.

Seven array elements can be driven at MO currents close to rollover for single mode operation. In contrast, devices 2, 3, 4, 6, 7, 11 and 13 show multimode emission when increasing the MO current beyond the values given in Fig. 3 and approaching the rollover current of the seed section. The DFB sections of devices 3, 4 and 13 exhibit lasing on both the low- and high-frequency DFB modes at high driving currents as a result of the influence of the back facet and/or the front facet. A representative spectrum is shown in Fig. 4(a) (device 13) from which one determines a photonic bandgap of 1.5 cm−1. For devices 2, 6, 7 and 11, the single mode operation of the DFB section at high MO currents is compromised either by side-modes close to the photonic bandgap, or by modes more than 10 cm−1 away from the Bragg wavenumber of the DFB grating.

In the regime of very low MO currents, the seeded mode is too weak to induce significant gain competition and efficiently suppress self-lasing of the amplifier section. The threshold for self-lasing of the PA on modes of the cavity formed either by the PA or both the MO and PA is influenced significantly by feedback from the MO and thus by losses or gain in this section. Compared to the case of an unpumped MO section, the losses determining the PA self-lasing threshold are reduced significantly when pumping the MO. At relatively low MO currents slightly above threshold, self-lasing of the PA thus sets already in around 5.2 A and dominates the LI curve, resulting in the linear characteristics expected for conventional lasers. This interpretation of the LI-curves for MO currents below 1 A is confirmed by the corresponding spectra presented for device 9 in Fig. 7
Fig. 7 Self-lasing of the power-amplifier at very low seed intensities for device 9. In addition to the high-frequency DFB mode (labeled 1), the red curve shows the appearance of FP modes of the amplifier section (labeled 3) at a low DFB current of 0.85 A and a high amplifier current of 6 A. The mode close to the lower edge of the photonic bandgap (labeled 2) is either the low-frequency DFB mode of the MO, or a self-lasing FP mode of the PA. At low MO currents, the intensity of the seeded mode is too weak to effectively suppress self-lasing of the PA section by gain competition. In contrast, for high DFB currents no PA self-lasing on additional modes is observed up to high amplifier currents, as shown in the inset.
. As seen in the inset of Fig. 7, for a high MO current the tapered section acts as an amplifier at a PA current of 6 A, resulting in single-mode emission of the MOPA. However, in case of very low MO currents, self-lasing of the the PA is observed for the same amplifier current of 6 A, with FP modes appearing around 1000 cm−1 (labeled 3 in Fig. 7). The additional mode (labeled 2) close to the high-frequencyDFB mode (1) could not be clearly identified, and either originates from self-lasing of the PA within the photonic bandgap close to its edge, or from lasing of the MO at the low-frequency DFB mode.

The clear signs of gain saturation seen in Fig. 6 imply that the performance of future MOPA arrays can be pushed towards higher output power by increasing the tapering angle of the PA section. For larger tapering angles, the mode seeded by the DFB section spreads adiabatically over a larger device cross-section while travelling through the amplifier, thus shifting the onset for gain saturation to higher powers. It is worth noting that an increase in the tapering angle for a given device length only increases the output power if the amplifier suffers from gain saturation.

Figure 8
Fig. 8 Angular in-plane distribution of the far-field intensity for all devices. The leftmost curve represents device 2 and the rightmost device 15. The devices were operated at maximum single-mode power, at the driving parameters given in Fig. 3, and thus correspond to the spectra shown in Fig. 2. The plots have been offset horizontally for clarity.
presents the far-field intensity distribution in the chip plane for each element of Array 2 which was measured using a HgCdTe detector mounted on a rotating arm at a distance of 18 cm from the device facets. During the experiment, the devices were driven under conditions for maximum single-mode power as given in Fig. 3. For all devices, a single-lobed far-field distribution is observed with only minor contributions by higher-order lateral modes for some array elements (6, 7, 8, 10 and 11). A single-lobed far-field distribution of Gaussian shape indicates the seeding of a single TM00 mode as well as the adiabatic spreading of the seeded mode during amplification. Figure 9(a)
Fig. 9 Angular in-plane distribution of the far-field intensity of Array 2 and typical light/DFB-current characteristics for Array 1 and 2 at constant amplifier current. a) The black and yellow curves highlight the minor contributions by higher-order lateral modes for two representative devices (11 and 8, respectively), where such contributions are observed for five of the array elements. The far-field of device 2, shown by the blue curve, is free of contributions by higher-order modes, as are the intensity distributions of nine devices at their maximum single-mode peak power. The red, dotted curve presents a Gaussian fitted to the blue curve. The angular intensity distribution of device 9 is shown by the green curve for a DFB/amplifier current of 2.3/9.5 A and at 10 W peak power, demonstrating the preservation of its excellent beam quality even at high output powers. b) On average, the elements of Array 1 exhibit a slightly lower slope efficiency than those of Array 2. Note that the slope of the presented curves is increased compared to the actual slope efficiency of the DFB section by the amplification factor associated with the power-amplifier.
compares the clean far-field distribution of device 2 and those of devices 8 and 11 which show higher-order-contributions. The dotted red curve represents a Gaussian fit of the far-field intensity distribution of device 2. As evident from this plot, the higher-order contributions observed for some of the devices are minor. All devices exhibit an in-plane far-field distribution with a FWHM between 6.8° and 8.2° with an average FWHM of 7.8°. These FWHM values compare well to the theoretical estimate of θ = 5.2° for the diffraction-limited in-plane divergence angle. This theoretical estimate was obtained by approximating the sinusoid in-plane field distribution of the amplifier mode at the facet by a Gaussian with an equivalent intensity standard deviation (Gaussian spot size of w0 = 39.6 μm) and using θ = 180°/π∙(2∙ln2)0.5∙λ /(π∙ w0) where λ is theaverage emission wavelength [18

18. A. Yariv and P. Yeh, Photonics: Optical Electronics in Modern Communications, 6th ed. (Oxford University Press, 2006), Chap. 16.

]. The green curve in Fig. 9 shows the far-field distribution of device 9 under driving conditions for 10 W peak power. While the intensity distribution at 10 W is slightly broader than that of the same device for 6.8 W, with a FWHM of 9° as compared to 8.2°, an excellent beam quality is maintained even at 10 W peak power. The single-lobed far-field plots in Fig. 8 demonstrate, together with the corresponding spectra shown in Fig. 2, that each element of Array 2 is capable of high-power operation while remaining single-mode in both the longitudinal and transverse dimensions.

4. Comparison between Arrays 1 and 2

As mentioned above, the array demonstrated in this work (Array 2) differs from that reported in reference [15

15. P. Rauter, S. Menzel, A. K. Goyal, B. Gökden, C. A. Wang, A. Sanchez, G. Turner, and F. Capasso, “Master-oscillator power-amplifier quantum cascade laser array,” Appl. Phys. Lett. 101(26), 261117 (2012). [CrossRef]

] (Array 1) in its DFB section design. For Array 1, a QWS was introduced in the DFB grating of each MO [15

15. P. Rauter, S. Menzel, A. K. Goyal, B. Gökden, C. A. Wang, A. Sanchez, G. Turner, and F. Capasso, “Master-oscillator power-amplifier quantum cascade laser array,” Appl. Phys. Lett. 101(26), 261117 (2012). [CrossRef]

] with the motivation of eliminating the uncertainty in the actual lasing wavelength. For applications requiring beam combining of the output of the array elements using a diffraction grating, a equidistant frequency spacing of the individual devices is essential [19

19. A. K. Goyal, M. Spencer, O. Shatrovoy, B. G. Lee, L. Diehl, C. Pfluegl, A. Sanchez, and F. Capasso, “Dispersion-compensated wavelength beam combining of quantum-cascade-laser arrays,” Opt. Express 19(27), 26725–26732 (2011). [CrossRef] [PubMed]

]. In work with diode lasers, DFB gratings with QWS have been investigated [20

20. K. Utaka, S. Akiba, K. Sakai, and Y. Matsushima, “λ/4-shifted InGaAsP/InP DFB lasers,” IEEE J. Quantum Electron. 22(7), 1042–1051 (1986). [CrossRef]

] for the same reason. The introduction of a QWS creates a defect state in the center of the photonic bandgap where the defect-state mode experiences significantly lower losses than the band-edge modes due to spatial confinement and the attendant less efficient out-coupling of its power.

5. Summary

In conclusion, we have demonstrated a high-power QCL MOPA array operating at fourteen different wavelengths between 9.2 and 9.8 μm. Each element is capable of single-mode operation (SMSR > 20 dB) at peak power values between 2.7 W and 10 W. The individual devices exhibit single-lobed far-field characteristics with an average FWHM angle of the narrow in-plane intensity distribution of 7.7°. With its high peak output power of several Watts per element (10 out of 14 devices were capable of peak powers between 3.9 and 10 W), clean single-mode spectra and excellent beam quality up to these high power values, the demonstrated QCL MOPA array is highly suitable as a source for stand-off detection and spectroscopy systems for a broad variety of applications from hazard detection to environmental studies.

Acknowledgments

References and links

1.

J. Faist, F. Capasso, D. L. Sivco, C. Sirtori, A. L. Hutchinson, and A. Y. Cho, “Quantum cascade laser,” Science 264(5158), 553–556 (1994). [CrossRef] [PubMed]

2.

C. Gmachl, F. Capasso, D. L. Sivco, and A. Y. Cho, “Recent progress in quantum cascade lasers and applications,” Rep. Prog. Phys. 64(11), 1533–1601 (2001). [CrossRef]

3.

A. K. Goyal, M. Spencer, M. Kelly, J. Costa, M. DiLiberto, E. Meyer, and T. Jeys, “Active infrared multispectral imaging of chemicals on surfaces,” Proc. SPIE 8018, 80180N, 80180N-11 (2011). [CrossRef]

4.

C. A. Kendziora, R. M. Jones, R. Furstenberg, M. Papantonakis, V. Nguyen, and R. A. McGill, “Infrared photothermal imaging for standoff detection applications,” Proc. SPIE 8373, 83732H, 83732H-10 (2012). [CrossRef]

5.

K. Degreif, S. Rademacher, P. Dasheva, F. Fuchs, S. Hugger, F. Schnürer, and W. Schweikert, “Stand-off explosive detection on surfaces using multispectral MIR-imaging,” Proc. SPIE 7945, 79450P, 79450P-8 (2011). [CrossRef]

6.

For a review on external cavity QCLs see:A. Hugi, R. Maulini, and J. Faist, “External cavity quantum cascade laser,” Semicond. Sci. Technol. 25(8), 083001 (2010). [CrossRef]

7.

B. G. Lee, M. A. Belkin, C. Pflügl, L. Diehl, H. A. Zhang, R. M. Audet, J. MacArthur, D. P. Bour, S. W. Corzine, G. E. Höfler, and F. Capasso, “DFB quantum cascade laser arrays,” IEEE J. Quantum Electron. 45(5), 554–565 (2009). [CrossRef]

8.

E. Mujagic, C. Schwarzer, Y. Yao, J. Chen, C. Gmachl, and G. Strasser, “Two-dimensional broadband distributed-feedback quantum cascade laser arrays,” Appl. Phys. Lett. 98(14), 141101 (2011). [CrossRef]

9.

Q. Y. Lu, Y. Bai, N. Bandyopadhyay, S. Slivken, and M. Razeghi, “2.4 W room temperature continuous wave operation of distributed feedback quantum cascade lasers,” Appl. Phys. Lett. 98(18), 181106 (2011). [CrossRef]

10.

H. Zhang, A. Seetharaman, P. Johnson, G. Luo, and H. Q. Le, “High-gain low-noise mid-infrared quantum cascade optical preamplifier for receiver,” IEEE Photon. Technol. Lett. 17(1), 13–15 (2005). [CrossRef]

11.

D. F. Welch, D. Mehuys, R. Parke, R. Waarts, D. Scifres, and W. Streifer, “Coherent operation of monolithically integrated master oscillator amplifiers,” Electron. Lett. 26(17), 1327–1329 (1990). [CrossRef]

12.

H. Wenzel, K. Paschke, O. Brox, F. Bugge, J. Fricke, A. Ginolas, A. Knauer, P. Ressel, and G. Erbert, “10W continuous-wave monolithically integrated master-oscillator power-amplifier,” Electron. Lett. 43(3), 160–161 (2007). [CrossRef]

13.

M. Troccoli, C. Gmachl, F. Capasso, D. L. Sivco, and A. Y. Cho, “Mid-infrared (λ~7.4µm) quantum cascade laser amplifier for high power single-mode emission and improved beam quality,” Appl. Phys. Lett. 80(22), 4103–4105 (2002). [CrossRef]

14.

S. Menzel, L. Diehl, C. Pflügl, A. Goyal, C. Wang, A. Sanchez, G. Turner, and F. Capasso, “Quantum cascade laser master-oscillator power-amplifier with 1.5 W output power at 300 K,” Opt. Express 19(17), 16229–16235 (2011). [CrossRef] [PubMed]

15.

P. Rauter, S. Menzel, A. K. Goyal, B. Gökden, C. A. Wang, A. Sanchez, G. Turner, and F. Capasso, “Master-oscillator power-amplifier quantum cascade laser array,” Appl. Phys. Lett. 101(26), 261117 (2012). [CrossRef]

16.

A. Wittmann, T. Gresch, E. Gini, L. Hvozdara, N. Hoyler, M. Giovannini, and J. Faist, “High-performance bound-to-continuum quantum-cascade laser for broad-gain applications,” IEEE J. Quantum Electron. 44(1), 36–40 (2008). [CrossRef]

17.

C. Pflügl, W. Schrenk, S. Anders, and G. Strasser, “Spectral dynamics of distributed feedback quantum cascade lasers,” Semicond. Sci. Technol. 19(4), S336–S338 (2004). [CrossRef]

18.

A. Yariv and P. Yeh, Photonics: Optical Electronics in Modern Communications, 6th ed. (Oxford University Press, 2006), Chap. 16.

19.

A. K. Goyal, M. Spencer, O. Shatrovoy, B. G. Lee, L. Diehl, C. Pfluegl, A. Sanchez, and F. Capasso, “Dispersion-compensated wavelength beam combining of quantum-cascade-laser arrays,” Opt. Express 19(27), 26725–26732 (2011). [CrossRef] [PubMed]

20.

K. Utaka, S. Akiba, K. Sakai, and Y. Matsushima, “λ/4-shifted InGaAsP/InP DFB lasers,” IEEE J. Quantum Electron. 22(7), 1042–1051 (1986). [CrossRef]

21.

M. Usami, S. Akiba, and K. Utaka, “Asymmetric λ/4-shifted InGaAsP/InP DFB lasers,” IEEE J. Quantum Electron. 23(6), 815–821 (1987). [CrossRef]

22.

G. Morthier and P. Vankenwinkelberge, “Handbook of distributed feedback laser diodes” (Artech House, 1997).

OCIS Codes
(140.3280) Lasers and laser optics : Laser amplifiers
(140.5965) Lasers and laser optics : Semiconductor lasers, quantum cascade

ToC Category:
Lasers and Laser Optics

History
Original Manuscript: December 21, 2012
Revised Manuscript: February 1, 2013
Manuscript Accepted: February 4, 2013
Published: February 13, 2013

Citation
Patrick Rauter, Stefan Menzel, Anish K. Goyal, Christine A. Wang, Antonio Sanchez, George Turner, and Federico Capasso, "High-power arrays of quantum cascade laser master-oscillator power-amplifiers," Opt. Express 21, 4518-4530 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-4-4518


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References

  1. J. Faist, F. Capasso, D. L. Sivco, C. Sirtori, A. L. Hutchinson, and A. Y. Cho, “Quantum cascade laser,” Science264(5158), 553–556 (1994). [CrossRef] [PubMed]
  2. C. Gmachl, F. Capasso, D. L. Sivco, and A. Y. Cho, “Recent progress in quantum cascade lasers and applications,” Rep. Prog. Phys.64(11), 1533–1601 (2001). [CrossRef]
  3. A. K. Goyal, M. Spencer, M. Kelly, J. Costa, M. DiLiberto, E. Meyer, and T. Jeys, “Active infrared multispectral imaging of chemicals on surfaces,” Proc. SPIE8018, 80180N, 80180N-11 (2011). [CrossRef]
  4. C. A. Kendziora, R. M. Jones, R. Furstenberg, M. Papantonakis, V. Nguyen, and R. A. McGill, “Infrared photothermal imaging for standoff detection applications,” Proc. SPIE8373, 83732H, 83732H-10 (2012). [CrossRef]
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  6. For a review on external cavity QCLs see:A. Hugi, R. Maulini, and J. Faist, “External cavity quantum cascade laser,” Semicond. Sci. Technol.25(8), 083001 (2010). [CrossRef]
  7. B. G. Lee, M. A. Belkin, C. Pflügl, L. Diehl, H. A. Zhang, R. M. Audet, J. MacArthur, D. P. Bour, S. W. Corzine, G. E. Höfler, and F. Capasso, “DFB quantum cascade laser arrays,” IEEE J. Quantum Electron.45(5), 554–565 (2009). [CrossRef]
  8. E. Mujagic, C. Schwarzer, Y. Yao, J. Chen, C. Gmachl, and G. Strasser, “Two-dimensional broadband distributed-feedback quantum cascade laser arrays,” Appl. Phys. Lett.98(14), 141101 (2011). [CrossRef]
  9. Q. Y. Lu, Y. Bai, N. Bandyopadhyay, S. Slivken, and M. Razeghi, “2.4 W room temperature continuous wave operation of distributed feedback quantum cascade lasers,” Appl. Phys. Lett.98(18), 181106 (2011). [CrossRef]
  10. H. Zhang, A. Seetharaman, P. Johnson, G. Luo, and H. Q. Le, “High-gain low-noise mid-infrared quantum cascade optical preamplifier for receiver,” IEEE Photon. Technol. Lett.17(1), 13–15 (2005). [CrossRef]
  11. D. F. Welch, D. Mehuys, R. Parke, R. Waarts, D. Scifres, and W. Streifer, “Coherent operation of monolithically integrated master oscillator amplifiers,” Electron. Lett.26(17), 1327–1329 (1990). [CrossRef]
  12. H. Wenzel, K. Paschke, O. Brox, F. Bugge, J. Fricke, A. Ginolas, A. Knauer, P. Ressel, and G. Erbert, “10W continuous-wave monolithically integrated master-oscillator power-amplifier,” Electron. Lett.43(3), 160–161 (2007). [CrossRef]
  13. M. Troccoli, C. Gmachl, F. Capasso, D. L. Sivco, and A. Y. Cho, “Mid-infrared (λ~7.4µm) quantum cascade laser amplifier for high power single-mode emission and improved beam quality,” Appl. Phys. Lett.80(22), 4103–4105 (2002). [CrossRef]
  14. S. Menzel, L. Diehl, C. Pflügl, A. Goyal, C. Wang, A. Sanchez, G. Turner, and F. Capasso, “Quantum cascade laser master-oscillator power-amplifier with 1.5 W output power at 300 K,” Opt. Express19(17), 16229–16235 (2011). [CrossRef] [PubMed]
  15. P. Rauter, S. Menzel, A. K. Goyal, B. Gökden, C. A. Wang, A. Sanchez, G. Turner, and F. Capasso, “Master-oscillator power-amplifier quantum cascade laser array,” Appl. Phys. Lett.101(26), 261117 (2012). [CrossRef]
  16. A. Wittmann, T. Gresch, E. Gini, L. Hvozdara, N. Hoyler, M. Giovannini, and J. Faist, “High-performance bound-to-continuum quantum-cascade laser for broad-gain applications,” IEEE J. Quantum Electron.44(1), 36–40 (2008). [CrossRef]
  17. C. Pflügl, W. Schrenk, S. Anders, and G. Strasser, “Spectral dynamics of distributed feedback quantum cascade lasers,” Semicond. Sci. Technol.19(4), S336–S338 (2004). [CrossRef]
  18. A. Yariv and P. Yeh, Photonics: Optical Electronics in Modern Communications, 6th ed. (Oxford University Press, 2006), Chap. 16.
  19. A. K. Goyal, M. Spencer, O. Shatrovoy, B. G. Lee, L. Diehl, C. Pfluegl, A. Sanchez, and F. Capasso, “Dispersion-compensated wavelength beam combining of quantum-cascade-laser arrays,” Opt. Express19(27), 26725–26732 (2011). [CrossRef] [PubMed]
  20. K. Utaka, S. Akiba, K. Sakai, and Y. Matsushima, “λ/4-shifted InGaAsP/InP DFB lasers,” IEEE J. Quantum Electron.22(7), 1042–1051 (1986). [CrossRef]
  21. M. Usami, S. Akiba, and K. Utaka, “Asymmetric λ/4-shifted InGaAsP/InP DFB lasers,” IEEE J. Quantum Electron.23(6), 815–821 (1987). [CrossRef]
  22. G. Morthier and P. Vankenwinkelberge, “Handbook of distributed feedback laser diodes” (Artech House, 1997).

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