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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 22, Iss. 6 — Mar. 24, 2014
  • pp: 6801–6809
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Mid-IR beam direction stabilization scheme for vibrational spectroscopy, including dual-frequency 2DIR

Clara M. Nyby, Joel D. Leger, Jianan Tang, Clyde Varner, Victor V. Kireev, and Igor V. Rubtsov  »View Author Affiliations


Optics Express, Vol. 22, Issue 6, pp. 6801-6809 (2014)
http://dx.doi.org/10.1364/OE.22.006801


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Abstract

A compact laser beam direction stabilization scheme is developed that provides the angular stability of better than 50 μrad over a wide range of frequencies from 800 to 4000 cm−1. The schematic is fully automated and features a single MCT quadrant detector. The schematic was tested to stabilize directions of the two IR beams used for dual-frequency two-dimensional infrared (2DIR) measurements and showed excellent results: automatic tuning of the beam direction allowed achieving the alignment quality within 10% of the optimal alignment obtained manually. The schematic can be easily implemented to any nonlinear spectroscopic measurements in the mid-IR spectral region.

© 2014 Optical Society of America

1. Introduction

A range of time-resolved vibrational spectroscopies have been under active development in recent years. Some of the techniques, such as methods of multidimensional infrared (IR) spectroscopy [1

1. R. M. Hochstrasser, “Two-dimensional spectroscopy at infrared and optical frequencies,” Proc. Natl. Acad. Sci. U.S.A. 104(36), 14190–14196 (2007). [CrossRef] [PubMed]

3

3. A. V. Pakoulev, M. A. Rickard, K. M. Kornau, N. A. Mathew, L. A. Yurs, S. B. Block, and J. C. Wright, “Mixed frequency-/time-domain coherent multidimensional spectroscopy: research tool or potential analytical method?” Acc. Chem. Res. 42(9), 1310–1321 (2009). [CrossRef] [PubMed]

], including fifth-order IR spectroscopies [4

4. S. Garrett-Roe and P. Hamm, “Purely absorptive three-dimensional infrared spectroscopy,” J. Chem. Phys. 130(16), 164510 (2009). [CrossRef] [PubMed]

, 5

5. E. C. Fulmer, F. Ding, and M. T. Zanni, “Heterodyned fifth-order 2D-IR spectroscopy of the azide ion in an ionic glass,” J. Chem. Phys. 122(3), 034302 (2005). [CrossRef] [PubMed]

], require spatial and time overlap of multiple mid-infrared (m-IR) pulses in the sample cell. Multiple-frequency techniques, such as dual-frequency two-dimensional infrared (DF 2DIR) require spatial overlap of the m-IR pulses of different central frequencies [6

6. I. V. Rubtsov, J. Wang, and R. M. Hochstrasser, “Dual-frequency 2D-IR spectroscopy heterodyned photon echo of the peptide bond,” Proc. Natl. Acad. Sci. U.S.A. 100(10), 5601–5606 (2003). [CrossRef] [PubMed]

, 7

7. Z. Lin, P. Keiffer, and I. V. Rubtsov, “A method for determining small anharmonicity values from 2DIR spectra using thermally induced shifts of frequencies of high-frequency modes,” J. Phys. Chem. B 115(18), 5347–5353 (2011). [CrossRef] [PubMed]

]. The power of the DF 2DIR can be fully realized only if the central frequencies of the m-IR pulses can be easily tuned to access a desired cross peak and the spatial overlap of the pulses in the sample is preserved with sufficient accuracy [8

8. S. R. Naraharisetty, V. M. Kasyanenko, and I. V. Rubtsov, “Bond connectivity measured via relaxation-assisted two-dimensional infrared spectroscopy,” J. Chem. Phys. 128(10), 104502 (2008). [CrossRef] [PubMed]

10

10. I. V. Rubtsov, “Energy transport in molecules studied by relaxation-assisted 2DIR spectroscopy,” in Ultrafast Infrared Vibrational Spectroscopy, M. Fayer, ed. (Taylor and Francis, 2013), pp. 333–359.

]. Note that femtosecond m-IR pulses are typically prepared via two sequential nonlinear processes, optical parametric generation/amplification and difference frequency generation (DFG). Several commercial computer-controlled optical parametric amplifiers (OPA) equipped with DFG units are available that can provide direction reproducibility of the m-IR output that can reach 1-2 mrad. However, to perform spectroscopic measurements, such as DF 2DIR, at least 20-fold higher angular stability is required [1

1. R. M. Hochstrasser, “Two-dimensional spectroscopy at infrared and optical frequencies,” Proc. Natl. Acad. Sci. U.S.A. 104(36), 14190–14196 (2007). [CrossRef] [PubMed]

, 6

6. I. V. Rubtsov, J. Wang, and R. M. Hochstrasser, “Dual-frequency 2D-IR spectroscopy heterodyned photon echo of the peptide bond,” Proc. Natl. Acad. Sci. U.S.A. 100(10), 5601–5606 (2003). [CrossRef] [PubMed]

]. Note that in DF 2DIR, for example, the 3rd-order signal depends crucially on the time delays between m-IR pulses, which makes manual spatial overlap optimization difficult due to delay changes introduced by angular tuning. Therefore, an automated schematic capable of reproducing the direction of a m-IR beam at different central frequencies over a three thousand wavenumber range is required for rapid 2DIR measurements over a broad range of frequencies.

A variety of active beam direction stabilization approaches were implemented for continuous-wave [11

11. S. Grafström, U. Harbarth, J. Kowalski, R. Neumann, and S. Noehte, “Fast laser beam position control with submicroradian precision,” Opt. Commun. 65(2), 121–126 (1988). [CrossRef]

] and pulsed lasers [12

12. A. Stalmashonak, N. Zhavoronkov, I. V. Hertel, S. Vetrov, and K. Schmid, “Spatial control of femtosecond laser system output with submicroradian accuracy,” Appl. Opt. 45(6), 1271–1274 (2006). [CrossRef] [PubMed]

17

17. A. A. Ageichik, V. I. Venglyuk, S. A. Dimakov, O. G. Kotyaev, V. P. Kalinin, V. L. Okulov, Y. A. Rezunkov, A. L. Safronov, G. Y. Snezhkov, G. A. Sokolova, A. N. Starchenko, V. V. Stepanov, A. P. Shestakov, M. P. Bogdanov, V. I. Kuprenyuk, A. Y. Rodionov, V. E. Sherstobitov, and V. V. Valuev, “Model experiments on position stabilization of a repetitively-pulsed CO2-laser beam on a distant detector with distortions in the propagation path,” J. Opt. Technol. 66(11), 945–953 (1999). [CrossRef]

]. The implemented approaches include single-point schemes to enhance laser pointing stability [13

13. A. Schwarz, M. Ueffing, Y. Deng, X. Gu, H. Fattahi, T. Metzger, M. Ossiander, F. Krausz, and R. Kienberger, “Active stabilization for optically synchronized optical parametric chirped pulse amplification,” Opt. Express 20(5), 5557–5565 (2012). [CrossRef] [PubMed]

, 14

14. T. Kanai, A. Suda, S. Bohman, M. Kaku, S. Yamaguchi, and K. Midorikawa, “Pointing stabilization of a high-repetition-rate high-power femtosecond laser for intense few-cycle pulse generation,” Appl. Phys. Lett. 92(6), 061106 (2008). [CrossRef]

], as well as two-point stabilization schemes [12

12. A. Stalmashonak, N. Zhavoronkov, I. V. Hertel, S. Vetrov, and K. Schmid, “Spatial control of femtosecond laser system output with submicroradian accuracy,” Appl. Opt. 45(6), 1271–1274 (2006). [CrossRef] [PubMed]

]. Fast-responding beam stabilization has been implemented for pulsed lasers in the visible and near-IR regions using position sensitive detectors [13

13. A. Schwarz, M. Ueffing, Y. Deng, X. Gu, H. Fattahi, T. Metzger, M. Ossiander, F. Krausz, and R. Kienberger, “Active stabilization for optically synchronized optical parametric chirped pulse amplification,” Opt. Express 20(5), 5557–5565 (2012). [CrossRef] [PubMed]

15

15. J. Liu, Y. Kida, T. Teramoto, and T. Kobayashi, “Generation of stable sub-10 fs pulses at 400 nm in a hollow fiber for UV pump-probe experiment,” Opt. Express 18(5), 4664–4672 (2010). [CrossRef] [PubMed]

] or CCD cameras [12

12. A. Stalmashonak, N. Zhavoronkov, I. V. Hertel, S. Vetrov, and K. Schmid, “Spatial control of femtosecond laser system output with submicroradian accuracy,” Appl. Opt. 45(6), 1271–1274 (2006). [CrossRef] [PubMed]

, 16

16. R. A. Hardin, Y. Liu, C. Long, A. Aleksandrov, and W. Blokland, “Active beam position stabilization of pulsed lasers for long-distance ion profile diagnostics at the Spallation Neutron Source (SNS),” Opt. Express 19(4), 2874–2885 (2011). [CrossRef] [PubMed]

]. Stabilization of a CO2 laser beam in turbulent atmosphere at distances of several km using a bright speckle method was reported [17

17. A. A. Ageichik, V. I. Venglyuk, S. A. Dimakov, O. G. Kotyaev, V. P. Kalinin, V. L. Okulov, Y. A. Rezunkov, A. L. Safronov, G. Y. Snezhkov, G. A. Sokolova, A. N. Starchenko, V. V. Stepanov, A. P. Shestakov, M. P. Bogdanov, V. I. Kuprenyuk, A. Y. Rodionov, V. E. Sherstobitov, and V. V. Valuev, “Model experiments on position stabilization of a repetitively-pulsed CO2-laser beam on a distant detector with distortions in the propagation path,” J. Opt. Technol. 66(11), 945–953 (1999). [CrossRef]

]. To the best of our knowledge, no beam direction stabilization scheme was reported for broad-range fs m-IR laser pulses.

Specific features of working in the m-IR region include relatively high pulse-to-pulse energy fluctuations, which can reach the level of several percent, inability to easily visualize the beam profile, and the necessity of changing the central frequency over a wide range from 800 to 4000 cm−1. Mid-IR cameras suitable for pulse imaging are available but prohibitively expensive. For operating with a broad range of frequencies, the beam stabilization schematic must be frequency insensitive. In addition, the m-IR beam diameter is frequency dependent, which imposes an additional constraint for the design of the schematic.

We report a design of an active beam direction stabilization scheme suitable for femtosecond m-IR laser pulses. The scheme can operate within a broad range of frequencies from 500 to 10000 cm−1, but has been tested for the narrower range from 800 to 4000 cm−1, where it provides stabilization accuracy of better than 50 μrad. Excellent performance of two such stabilization schemes was demonstrated within a recently developed fully automated dual-frequency three-pulse 2DIR instrument with heterodyned detection.

2. Results and discussion

To generate m-IR pulses, a Ti:Sapphire laser (Libra, Coherent), producing 1.5 W power at 1 kHz repetition rate with 80 fs pulse duration at 800 nm, was used to pump two OPAs (Palitra-duo, Quantronix). Each OPA output was directed to a non-collinear difference frequency generation (DFG) unit (Quantronix), featuring AgGaS2 (nIR1) and AgGaSe2 (nIR2) crystals. The resulting m-IR beam is collimated and has the pulse energy ranging from 2 to 10 µJ and beam diameter ranging from 2 to 4.5 mm. Both the OPA and DFG instruments are fully computer controlled. The pointing stability of the m-IR output can be adjusted and optimized, but generally is limited to ca. 1 mrad. A liquid-nitrogen cooled HgCdTe (MCT) quadrant (quad) detector (Infrared Associates Inc.) is used as a position sensitive element. The detector has a peak sensitivity of ca. 10 μm, which results in a cut-off wavelength exceeding 12.5 μm. The quad detector has four elements, 2 x 2 mm each, with a gap of ca. 50 μm. There is a small crosstalk between the channels; it is less than 3% for one quad detector and less than 6.3% for another quad. However, no influence of the crosstalk on the overall device operation was found – the two quads with about twice different crosstalk values behave similarly well.

2.1. Design of the schematics

The principles of active beam direction stabilization schematics have been reported previously [11

11. S. Grafström, U. Harbarth, J. Kowalski, R. Neumann, and S. Noehte, “Fast laser beam position control with submicroradian precision,” Opt. Commun. 65(2), 121–126 (1988). [CrossRef]

]. The schematics are based on the idea of recovering the beam either in two points along its path or recovering a point and the propagation angle. For broad-band frequency applications, care must be taken to ensure independence of the recovered beam direction from the radiation wavelength. For that reason, the schematic developed uses a single beam sampler (W1) to generate both points along the sampled beam direction that is a conjugate to the direction of the main beam (Fig. 1).
Fig. 1 Optical schematic of the beam stabilization unit. The computer (PC) controlled elements are indicated by thin black lines connected to the PC. Here M is a computer controlled mirror, W is a wedge, L is a lens, F is a filter, BS is a beam splitter, Quad is a quad detector, and A is an aperture.
The beam sampler W1, wedged uncoated ZnSe window (II-VI Infrared, 25 mm in diameter), is placed at an angle that is close to the Brewster angle to minimize the power losses. The actual incidence angle was ca. 57 degrees, which results in ca. 2.8% reflectivity per surface and overall losses of ca. 11%, but supports a transmission aperture of 12 mm with 1” optics. The wedge angle, 1 degree, was selected to be large enough to separate the reflections from the two surfaces at a reasonably short distance. The second wedged window (W2) is placed after the first one at a short distance (45 mm) to compensate for the spatial dispersion (Fig. 1). The sampled beam reflected from the first surface of W1 is directed to a ZnSe uncoated plano-convex lens of a focal length of f = 100 mm, which serves as a beam splitter. The transmitted beam (b1) is directed at the detector, while the beam reflected from the flat front surface (b2, ca. 17% reflected) passes some distance, and is also directed onto the same quad detector. The distance of 0.68 m between two stabilization points is large enough to ensure high stabilization accuracy while maintaining a compact design. A 50:50 beam splitter (BS) on a ZnSe substrate (Tydex) is used to combine the two beams along the same direction.

Another specific aspect of the m-IR application is that the MCT quad detectors are expensive and require liquid nitrogen for cooling. It is advantageous to use a single quad detector in the beam stabilization schematics. A computer-controlled flipper selects which beam is measured by the quad detector. Two computer controlled mirrors (M1, M2) placed before the wedges are used to direct the beam into place. The lens position is selected so that the spot of the m-IR beam at the M2 mirror is imaged at the quad detector; the distance between M2 and the quad is ca. 4f. M1 tuning recovers the beam spot position on the M2 mirror by centering b1 at the quad detector. During the M1 tuning, the flipper blocks the b2 beam. In the second step, the beam b1 is blocked by the flipper and the beam b2 is directed to the center of the quad detector by tuning M2, recovering the direction of the sampled beam, thus recovering the direction of the main m-IR beam. The distance between M2 and the detector of ca. 0.68 m permits for sufficient accuracy of the recovered angle. The schematic shown in Fig. 1 is modular, built on a common vertically positioned metal plate of ca. 15 x 15 cm. Two apertures, A1 and A2, are used for initial alignment of the scheme using a Helium-Neon laser (HeNe). To install the scheme into the m-IR beam, the m-IR beam is centered at A1 and A2 apertures using a power meter, and then the quad detector is centered at the beam b1. The beam b2 is then directed to the center of the detector by the last mirror in its path; since the scheme is pre-aligned using HeNe, only small corrections are needed when setting it for a m-IR beam. The apertures A1 and A2 are fully opened during the m-IR operation. The flipper is capable of blocking both beams at the same time for measuring the background counts from the detector. A neutral density filter and a filter to cut Signal and Idler beams are placed in front of the detector (F).

2.2. Computer program controlling the measurements

The system includes several computer-controlled elements that measure and control the beam direction. The M1 and M2 mirrors are controlled by linear actuators (Picomotor piezo, Newport). These actuators have a linear drive resolution of 30 nm, which translates to an angular step of about 1 μrad when driving a 1” mirror. A microcontroller board (Arduino Uno, Adafruit Industries), connected to a computer through a USB port, controls a rotational stage (Micro Servo, Adafruit Industries), which serves as a flipper. Three positions are executed by the flipper: two where the flipper allows either beam b1 or b2 for measurements of the respective stabilization point, and a third where it blocks both beams, which is used for measuring the background signal. The Femtosecond Laser Pulse Acquisition System (FPAS-1600) box-car integrator (Infrared Systems Development Co.) measures all four detector signals of the MCT quadrant detector for each laser pulse. The data are transferred from the FPAS to the computer via a National Instruments PCI 6533 card.

A C++ program controls the computer-controlled elements of the system and automatically stabilizes the beam direction. For each stabilization point, the deviation in the x direction is calculated as the normalized difference of the beam intensity on the two left-hand quadrants and that on the two right-hand quadrants. Similarly, the deviation in the y direction is calculated from the difference of the beam intensity on the two upper quadrants and that on the two lower quadrants. The deviation is calculated for each laser shot and averaged for Nacc laser shots. A beam-size parameter accounts for the dependence of the calculated deviation on the beam size. From the deviation, the program calculates the correction shifts needed and directs the motorized mirror accordingly. When a user-selected tolerance is reached in both the x- and y-directions, the program switches the stabilization point by changing the flipper position and resumes stabilizing. The approach of the point to the target position follows a gradient descent algorithm such that several steps are required to reach stabilization within the tolerance. Typical stabilization requires about 1-2 minutes, which includes several iterations of stabilizing both the first and second points. The same computer program controls two beam stabilization schematics.

2.3. Testing scheme performance

The schematic was tested in the following ways: First, reproducibility of beam stabilization was tested at various fixed wavelengths. Second, the beam stabilization scheme was tested by switching between different wavelengths. Third, two such schematics were tested within a dual-frequency three-pulse photon-echo 2DIR setup.

Reproducibility at specific wavelengths

For this test, the beam direction reproducibility was judged by the direction of a HeNe beam co-propagating with the m-IR beam on which stabilization was executed. The HeNe beam spot position was recorded at a large distance from the beam stabilization scheme. The m-IR beam direction (and co-propagating HeNe) was then disturbed prior to mirror M1 and beam stabilization was executed again. Small but measurable deviations were recorded at the distance of 8.4 m where the HeNe beam diameter was ca. 3 mm. The experiment was repeated over 5 times at each wavelength and the angular deviation, σθ (STD), was determined. Table 1 shows σθ obtained at several m-IR frequencies. The σθ values vary in the range of 17 – 47 μrad.

Table 1. Beam deviations recorded at various wavelengths performing a disturb-stabilize cycle.

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There are several factors affecting the quality of beam stabilization of m-IR pulses, such as beam fluctuations and beam diameter.

The m-IR beam fluctuations include pulse-to-pulse energy and beam profile fluctuations. These fluctuations are the main factors affecting the beam stabilization quality. Note that the beam profile fluctuations include beam position and beam angle fluctuations, as well as the beam transversal quality, the intensity fluctuations within the same cross-section. Longer pulse-averaging helps suppress fast laser fluctuations, but slow fluctuations will still affect the stabilization quality. Averaging of Nacc = 500 laser shots was routinely used in this work. The beam center was determined for every laser pulse and the x and y widths of the beam-center distribution, σx and σy (STD), were computed using Nacc accumulations. The σx and σy values determined for the 1st and 2nd stabilization points along the beam generally determine the accuracy of the beam stabilization. The stabilization tolerance was chosen to be ca. 30% smaller than the σx and σy values. A comparison of the σx and σy values for the 1st and the 2nd stabilization points permits determining if the angular fluctuations are the dominant fluctuations; a substantially larger σx and σy should be observed for the 2nd point in this case. The experimental results show that the angular fluctuations are not dominant, but certainly contributing to the overall fluctuations. For example, for the beam at 3850 cm−1 (Table 1) the spatial fluctuations at the 1st point were ca. 8 and 13 μm (σx and σy), while those for the 2nd point, which is ca. 0.68 m apart from the 1st point, were 10 and 20 μm. Note that the scales of the deviations, different for the 1st and 2nd points, were carefully calibrated in μm for these measurements. The σx and σy values at the 1st and 2nd stabilization points give a rough estimate of the angular deviations that can be reached for a particular m-IR beam: for the example above, the overall shift of 13 plus 20 μm at 0.68 m distance gives the angular accuracy of 49 μrad, which is expected to be (and is) larger than the measured angular deviations of 17-30 μrad (Table 1) due to a neglect of the correlated deviations at the 1st and 2nd stabilization points in such simplified estimation. Nevertheless, these measurements give an understanding of the origin of the limitations for the beam stabilization accuracy.

The shot-to-shot m-IR energy fluctuations are expected to minimally affect the measured beam center, as the beam center, calculated for each laser shot, is not very sensitive to the pulse energy. Note that the background at each element of the quad detector was accurately measured and subtracted. The actual level of the m-IR energy fluctuations during the measurements was ca. 1-2%.

Another factor affecting the performance is the quality of the beam profile; because the beam profile is non-ideal, the performance also depends on the beam size. When the beam size is approaching the overall size of the quad detector, the sensitivity to the beam center position decreases, while the sensitivity to the beam non-uniformity increases. For the 4 x 4 mm quad detector used in this work we found that the stabilization accuracy decreases about two-fold when the beam size is ca. 3.7-3.8 mm, compared to the accuracy for the beams smaller than 3 mm. For example, at 3850 cm−1 the standard deviation of 29 μrad was found for the 2.8 beam diameter, which increased to 47 μrad when the diameter was increased to 3.7 mm (these experiments were done back-to-back so the beam profile was the same). For the beams exceeding 4.5 mm in diameter, the stabilization accuracy drops further and, for the level of beam fluctuations in our m-IR pulses, becomes practically unusable. However, reproducible stabilization was observed when an aperture of ca. 3 mm was placed into the beam before the beam stabilization scheme (909 cm−1, Table 1). However, for good results, the aperture has to be well centered on the beam, which requires manual intrusion.

Direction stability when switching between wavelengths

The beam profile was recorded by razor-blade edge profiling performed in the focus of a 90° parabolic gold-coated reflector with effective focal length of 105 mm (Thorlabs). The beam center shift was recorded for every experiment by the least-squared deviation fitting of the normalized S-shaped profiles (Fig. 2).
Fig. 2 The beam diameters were 2.8, 2.9, and 3.0 μm at 3850, 2000, 1250 cm−1 respectively.
The results are summarized in Table 2.

Table 2. Beam deviations when switching between different frequencies.

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For example, there is only a 0.1 μm beam shift when the frequency is switched from 2000 to 1250 cm−1. The maximum beam shift of 6.0 μm observed when switching from 3850 cm−1 to 1250 cm−1 illustrates the accuracy of the stabilization across this tuning range. The shift is much smaller than the beam waist (~150 μm) and such accuracy is therefore sufficient for spectroscopic measurements in the m-IR region.

Deviation errors obtained for individual wavelengths can be compared to the angular deviations obtained using the HeNe beam. The standard deviation, σx, represents the accuracy of stabilizing on each frequency. For example, for the beam at 3850 cm−1, σx of 1.2 μm (Table 2) measured in the focus of 105 mm parabolic reflector corresponds to the angular deviation of 11 μrad, which is close to the value of 17 μrad obtained using the HeNe beam (Table 1).

Testing the beam stabilization scheme within dual-frequency 2DIR instrument

The main m-IR beam passes through two wedges W1 and W2, which results in its shift in the incidence plane. The value of the shift depends on the beam incidence angle and the distance between the two wedges. For the incidence angle of 57 degrees, the wedge thickness of 3.05 mm, and the wedge separation of 40 mm, the shift is ca. 1.2 mm. Because the index of refraction of ZnSe varies with wavelength (from ca. 2.44 to 2.39 for 4000 to 800 µm, respectively) the shift is frequency dependent. To preserve the frequency insensitivity of the stabilization schematic, the dispersion of the shift has to be compensated. In fact, if there are other elements in the beam that produce frequency-sensitive deviations, those deviations need to be compensated as well. The most critical parameter affecting the dispersion introduced by the wedges is the distance between them. The residual dispersion can be compensated by introducing another ZnSe window at the Brewster angle.

While for ideal performance of the beam stabilization device it is important to compensate the frequency-dependent beam shift, such shift is not essential for majority of spectroscopic applications in the m-IR, as the beam overlap is typically achieved in the beam focus, where the shift has no effect. Such is the case for dual-frequency 2DIR spectroscopy, where all beams are focused in the sample cell, typically by a parabolic reflector. For example, a vertical shift of beams 1 and 2 (Fig. 3) would not alter their mutual overlap and the overlap with beam 3.

The use of a single quad detector significantly simplifies the beam stabilization device and reduces its cost. At the same time, it makes any real-time tracking of the beam direction difficult. A relatively high shot-to-shot noise of m-IR pulses may make fast and accurate beam tracking problematic. The device can be easily modified to work with m-IR beams of larger diameter by either using larger size detectors or by using lenses. A compression of the image can be performed for the 1st stabilization point, while a long-focal length lens can be used for the 2nd stabilization point with the detector in its focus. Note, however, that there is a 50 μm gap between the elements of the quad detector, so the beam size in the focus should be much larger than the gap.

3. Conclusions

A compact beam direction stabilization scheme suitable for femtosecond m-IR laser pulses is reported. The scheme is fully automated and works for a broad range of m-IR frequencies, tested from 800 to 4000 cm−1, where the direction accuracy of better than 50 μrad is achieved. Spatial deviation of less than 6 μm in the focus of the parabolic reflector of 105 mm effective focal length is achieved when tuning the frequency over this spectral range. The range of the beam diameters suitable for direction stabilization is limited by the size of the quad detector and by sizes of other optical elements used in the scheme. The constructed schematic, featuring a quad detector with the element size of 2 x 2 mm, works well with beam diameters not exceeding 4.0 mm. The schematic has a small footprint of ca. 7 x 15 cm2 (excluding the size of the quad detector) and can therefore be easily incorporated into various spectroscopic setups and instruments. Excellent performance of two such stabilization schemes was demonstrated within a recently developed fully automated dual-frequency three-pulse 2DIR instrument with heterodyned detection.

Acknowledgments

Support by the National Science Foundation (CHE-1040491) is gratefully acknowledged. The Louisiana Board of Regents (Grant LEQSF(2011-12)-ENH-TR-29) is thanked for supporting the acquisition of the fs Ti:Sapphire laser system.

References and Links

1.

R. M. Hochstrasser, “Two-dimensional spectroscopy at infrared and optical frequencies,” Proc. Natl. Acad. Sci. U.S.A. 104(36), 14190–14196 (2007). [CrossRef] [PubMed]

2.

J. Zheng and M. D. Fayer, “Solute-solvent complex kinetics and thermodynamics probed by 2D-IR vibrational echo chemical exchange spectroscopy,” J. Phys. Chem. B 112(33), 10221–10227 (2008). [CrossRef] [PubMed]

3.

A. V. Pakoulev, M. A. Rickard, K. M. Kornau, N. A. Mathew, L. A. Yurs, S. B. Block, and J. C. Wright, “Mixed frequency-/time-domain coherent multidimensional spectroscopy: research tool or potential analytical method?” Acc. Chem. Res. 42(9), 1310–1321 (2009). [CrossRef] [PubMed]

4.

S. Garrett-Roe and P. Hamm, “Purely absorptive three-dimensional infrared spectroscopy,” J. Chem. Phys. 130(16), 164510 (2009). [CrossRef] [PubMed]

5.

E. C. Fulmer, F. Ding, and M. T. Zanni, “Heterodyned fifth-order 2D-IR spectroscopy of the azide ion in an ionic glass,” J. Chem. Phys. 122(3), 034302 (2005). [CrossRef] [PubMed]

6.

I. V. Rubtsov, J. Wang, and R. M. Hochstrasser, “Dual-frequency 2D-IR spectroscopy heterodyned photon echo of the peptide bond,” Proc. Natl. Acad. Sci. U.S.A. 100(10), 5601–5606 (2003). [CrossRef] [PubMed]

7.

Z. Lin, P. Keiffer, and I. V. Rubtsov, “A method for determining small anharmonicity values from 2DIR spectra using thermally induced shifts of frequencies of high-frequency modes,” J. Phys. Chem. B 115(18), 5347–5353 (2011). [CrossRef] [PubMed]

8.

S. R. Naraharisetty, V. M. Kasyanenko, and I. V. Rubtsov, “Bond connectivity measured via relaxation-assisted two-dimensional infrared spectroscopy,” J. Chem. Phys. 128(10), 104502 (2008). [CrossRef] [PubMed]

9.

Z. Lin, B. Bendiak, and I. V. Rubtsov, “Discrimination between coupling networks of glucopyranosides varying at a single stereocenter using two-dimensional vibrational correlation spectroscopy,” Phys. Chem. Chem. Phys. 14(18), 6179–6191 (2012). [CrossRef] [PubMed]

10.

I. V. Rubtsov, “Energy transport in molecules studied by relaxation-assisted 2DIR spectroscopy,” in Ultrafast Infrared Vibrational Spectroscopy, M. Fayer, ed. (Taylor and Francis, 2013), pp. 333–359.

11.

S. Grafström, U. Harbarth, J. Kowalski, R. Neumann, and S. Noehte, “Fast laser beam position control with submicroradian precision,” Opt. Commun. 65(2), 121–126 (1988). [CrossRef]

12.

A. Stalmashonak, N. Zhavoronkov, I. V. Hertel, S. Vetrov, and K. Schmid, “Spatial control of femtosecond laser system output with submicroradian accuracy,” Appl. Opt. 45(6), 1271–1274 (2006). [CrossRef] [PubMed]

13.

A. Schwarz, M. Ueffing, Y. Deng, X. Gu, H. Fattahi, T. Metzger, M. Ossiander, F. Krausz, and R. Kienberger, “Active stabilization for optically synchronized optical parametric chirped pulse amplification,” Opt. Express 20(5), 5557–5565 (2012). [CrossRef] [PubMed]

14.

T. Kanai, A. Suda, S. Bohman, M. Kaku, S. Yamaguchi, and K. Midorikawa, “Pointing stabilization of a high-repetition-rate high-power femtosecond laser for intense few-cycle pulse generation,” Appl. Phys. Lett. 92(6), 061106 (2008). [CrossRef]

15.

J. Liu, Y. Kida, T. Teramoto, and T. Kobayashi, “Generation of stable sub-10 fs pulses at 400 nm in a hollow fiber for UV pump-probe experiment,” Opt. Express 18(5), 4664–4672 (2010). [CrossRef] [PubMed]

16.

R. A. Hardin, Y. Liu, C. Long, A. Aleksandrov, and W. Blokland, “Active beam position stabilization of pulsed lasers for long-distance ion profile diagnostics at the Spallation Neutron Source (SNS),” Opt. Express 19(4), 2874–2885 (2011). [CrossRef] [PubMed]

17.

A. A. Ageichik, V. I. Venglyuk, S. A. Dimakov, O. G. Kotyaev, V. P. Kalinin, V. L. Okulov, Y. A. Rezunkov, A. L. Safronov, G. Y. Snezhkov, G. A. Sokolova, A. N. Starchenko, V. V. Stepanov, A. P. Shestakov, M. P. Bogdanov, V. I. Kuprenyuk, A. Y. Rodionov, V. E. Sherstobitov, and V. V. Valuev, “Model experiments on position stabilization of a repetitively-pulsed CO2-laser beam on a distant detector with distortions in the propagation path,” J. Opt. Technol. 66(11), 945–953 (1999). [CrossRef]

18.

V. M. Kasyanenko, S. L. Tesar, G. I. Rubtsov, A. L. Burin, and I. V. Rubtsov, “Structure dependent energy transport: Relaxation-assisted 2DIR measurements and theoretical studies,” J. Phys. Chem. B 115(38), 11063–11073 (2011). [CrossRef] [PubMed]

OCIS Codes
(120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
(120.4570) Instrumentation, measurement, and metrology : Optical design of instruments
(140.3425) Lasers and laser optics : Laser stabilization

ToC Category:
Spectroscopy

History
Original Manuscript: December 26, 2013
Revised Manuscript: January 29, 2014
Manuscript Accepted: February 10, 2014
Published: March 17, 2014

Citation
Clara M. Nyby, Joel D. Leger, Jianan Tang, Clyde Varner, Victor V. Kireev, and Igor V. Rubtsov, "Mid-IR beam direction stabilization scheme for vibrational spectroscopy, including dual-frequency 2DIR," Opt. Express 22, 6801-6809 (2014)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-6-6801


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References

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  9. Z. Lin, B. Bendiak, I. V. Rubtsov, “Discrimination between coupling networks of glucopyranosides varying at a single stereocenter using two-dimensional vibrational correlation spectroscopy,” Phys. Chem. Chem. Phys. 14(18), 6179–6191 (2012). [CrossRef] [PubMed]
  10. I. V. Rubtsov, “Energy transport in molecules studied by relaxation-assisted 2DIR spectroscopy,” in Ultrafast Infrared Vibrational Spectroscopy, M. Fayer, ed. (Taylor and Francis, 2013), pp. 333–359.
  11. S. Grafström, U. Harbarth, J. Kowalski, R. Neumann, S. Noehte, “Fast laser beam position control with submicroradian precision,” Opt. Commun. 65(2), 121–126 (1988). [CrossRef]
  12. A. Stalmashonak, N. Zhavoronkov, I. V. Hertel, S. Vetrov, K. Schmid, “Spatial control of femtosecond laser system output with submicroradian accuracy,” Appl. Opt. 45(6), 1271–1274 (2006). [CrossRef] [PubMed]
  13. A. Schwarz, M. Ueffing, Y. Deng, X. Gu, H. Fattahi, T. Metzger, M. Ossiander, F. Krausz, R. Kienberger, “Active stabilization for optically synchronized optical parametric chirped pulse amplification,” Opt. Express 20(5), 5557–5565 (2012). [CrossRef] [PubMed]
  14. T. Kanai, A. Suda, S. Bohman, M. Kaku, S. Yamaguchi, K. Midorikawa, “Pointing stabilization of a high-repetition-rate high-power femtosecond laser for intense few-cycle pulse generation,” Appl. Phys. Lett. 92(6), 061106 (2008). [CrossRef]
  15. J. Liu, Y. Kida, T. Teramoto, T. Kobayashi, “Generation of stable sub-10 fs pulses at 400 nm in a hollow fiber for UV pump-probe experiment,” Opt. Express 18(5), 4664–4672 (2010). [CrossRef] [PubMed]
  16. R. A. Hardin, Y. Liu, C. Long, A. Aleksandrov, W. Blokland, “Active beam position stabilization of pulsed lasers for long-distance ion profile diagnostics at the Spallation Neutron Source (SNS),” Opt. Express 19(4), 2874–2885 (2011). [CrossRef] [PubMed]
  17. A. A. Ageichik, V. I. Venglyuk, S. A. Dimakov, O. G. Kotyaev, V. P. Kalinin, V. L. Okulov, Y. A. Rezunkov, A. L. Safronov, G. Y. Snezhkov, G. A. Sokolova, A. N. Starchenko, V. V. Stepanov, A. P. Shestakov, M. P. Bogdanov, V. I. Kuprenyuk, A. Y. Rodionov, V. E. Sherstobitov, V. V. Valuev, “Model experiments on position stabilization of a repetitively-pulsed CO2-laser beam on a distant detector with distortions in the propagation path,” J. Opt. Technol. 66(11), 945–953 (1999). [CrossRef]
  18. V. M. Kasyanenko, S. L. Tesar, G. I. Rubtsov, A. L. Burin, I. V. Rubtsov, “Structure dependent energy transport: Relaxation-assisted 2DIR measurements and theoretical studies,” J. Phys. Chem. B 115(38), 11063–11073 (2011). [CrossRef] [PubMed]

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