Nonlinear optical techniques are widely used to study energy transport in nanoscale objects. In particular photon echo spectroscopy can be used to determine if the energy transport is coherent or not. In this project a novel phase sensitive nonlinear technique is proposed. The main feature of this technique is the application of two phase-locked pulses. The relative phase and the delay between the two pulses is set electronically by a pulse shaper based on a spatial light modulator (SLM). The use of an SLM ensures phase stability. The proposed method is tested on a model system of solutions of the dye molecule DTTCI in ethylene glycol and acetonitrile. The obtained results demonstrated that the parameters from the experimental data agree with those from previous studies. Hence, the proposed technique can be further developed for energy transport studies.
Nonlinear optical techniques are widely used to study energy transport in nanoscale objects. In particular photon echo spectroscopy can be used to determine if the energy transport is coherent or not. In this project a novel phase sensitive nonlinear technique is proposed. The main feature of this technique is the application of two phase-locked pulses. The relative phase and the delay between the two pulses is set electronically by a pulse shaper based on a spatial light modulator (SLM). The use of an SLM ensures phase stability. The proposed method is tested on a model system of solutions of the dye molecule DTTCI in ethylene glycol and acetonitrile. The obtained results demonstrated that the parameters from the experimental data agree with those from previous studies. Hence, the proposed technique can be further developed for energy transport studies.
Optical two-dimensional photon-echo spectroscopy is realized with shaped excitation pulses, allowing coherent control of twodimensional spectra. This development enables probing of state-selective quantum decoherence and phase/time sensitive couplings between states. The coherently-controlled two-dimensional photon-echo spectrometer with two pulse shapers is based on a passively stabilized four-beam interferometer with diffractive optic, and allows heterodyne detection of signals with a long-term phase stability of approximately Lambda/100. The two-dimensional spectra of Rhodamine 101 in a methanol solution, measured with unshaped and shaped pulses, exhibit significant differences. We observe in particular, the appearance of fine structure in the spectra obtained using shaped excitation pulses.
In this series of papers we report on the generation and application of multiple pulse phase coherent sequences in optical spectroscopy.In this paper the effects of intense pulse trains on systems with only two resonant energy levels are analyzed, with particular attention to the effects of extreme inhomogeneous broadening and population depletion to nonresonant levels.It is shown that these effects, which are present in virtually all optical systems, make the simple gyroscopic model of optical coherent transients invalid.Exact calculations show, e.g., that a two-pulse photon echo is not maximized by a 1:2 length ratio for the pulses; that the maximum excited state population is not created by a 180" pulse; and that three equal pulses are almost as effective as a 1:2:1 ratio for producing three pulse echoes.The role of pulse phase is extensively analyzed.Pulse sequences are proposed and experimentally demonstrated which permit optical phase sensitive detection and measurement of ground state relaxation parameters.The experimental results are based on an extension of the acousto-optic modulation and fluoresence detection techniques of Zewail and Orlowski [Zewail et al., Chem.Phys.Lett.48, 256 (1977); Orlowski et al., ibid.54, 197 (1978)).The relative merits offluorescence and transverse polarization detection are discussed, and fluorescence detection is shown to be more generally useful for these new sequences.Finally, composite pulse trains are shown to be capable of substantially increasing the signal available from highly inhomogenously broadened transitions.In paper II we extend the treatment to multilevel systems with some emphasis on solid state applications.
The use of phase-locked pulses in various spectroscopic techniques related to the third-order polarization P(3) is analyzed. Using correlation function expressions for the nonlinear response function, we clarify the interrelationship among several photon echo, pump–probe, and spontaneous light emission techniques, without alluding to any specific model for the material system. By combining phase-locked pulses and heterodyne detection it becomes possible to probe separately the real and imaginary parts of the nonlinear response function. Combining two phase-locked pulse excitation with time-resolved detection of the spontaneous light emission allows direct separation of the Raman and fluorescence contributions.
A new method for waveform measurement of photon echoes using a modified Michelson interferometer has been developed. The experimental setup uses collinear geometry, and photon echo signals are detected using a double-phase modulation technique. The amplitude and phase of photon echoes and those of excitation pulses are simultaneously measured by this technique. The method has been applied to a photon echo experiment on a dye solution. The results are explained using a stochastic modulation model with an accumulation effect of population grating.
In this series of papers we report on the generation and application of multiple pulse phase coherent sequences in optical spectroscopy. In this paper the effects of intense pulse trains on systems with only two resonant energy levels are analyzed, with particular attention to the effects of extreme inhomogeneous broadening and population depletion to nonresonant levels. It is shown that these effects, which are present in virtually all optical systems, make the simple gyroscopic model of optical coherent transients invalid. Exact calculations show, e.g., that a two-pulse photon echo is not maximized by a 1:2 length ratio for the pulses; that the maximum excited state population is not created by a 180° pulse; and that three equal pulses are almost as effective as a 1:2:1 ratio for producing three pulse echoes. The role of pulse phase is extensively analyzed. Pulse sequences are proposed and experimentally demonstrated which permit optical phase sensitive detection and measurement of ground state relaxation parameters. The experimental results are based on an extension of the acousto-optic modulation and fluoresence detection techniques of Zewail and Orlowski [Zewail et al., Chem. Phys. Lett. 48, 256 (1977); Orlowski et al., ibid. 54, 197 (1978)]. The relative merits of fluorescence and transverse polarization detection are discussed, and fluorescence detection is shown to be more generally useful for these new sequences. Finally, composite pulse trains are shown to be capable of substantially increasing the signal available from highly inhomogenously broadened transitions. In paper II we extend the treatment to multilevel systems with some emphasis on solid state applications.
We extend our theoretical framework for time-resolved nonlinear microspectroscopy [M. Cho, J. Chem. Phys. 162, 124201 (2025)] to coherent four-wave-mixing spectroscopy using paraxial Laguerre-Gaussian (LG) beams. Unlike pump-probe or transient absorption techniques, photon echo is highly sensitive to the spatial phase structure of LG beams. This sensitivity arises because coherence evolution in inhomogeneously broadened absorbers depends on the radial and azimuthal indices of the LG modes used in the write-and-read processes within the photon echo configuration. Recent advances in spatial light modulators, metasurfaces, and ultrafast laser techniques have significantly improved spatial and temporal control over quantum materials. These innovations enable new approaches to studying heterogeneous systems, developing multidimensional microspectroscopy, and exploring alternative quantum information storage methods. In this work, we investigate photon echo signals generated by LG beams and derive analytical expressions for rephasing and non-rephasing photon echoes. Our results reveal how beam parameters influence nonlinear spatiotemporal responses, capturing spatial variations in pulse amplitudes, phases, and inhomogeneity-induced dephasing and rephasing. We show that customized ultrafast pulses and structured spatial light fields can enhance the spatial separation of photon echo signals and increase the density of stored quantum information. This work advances nonlinear molecular spectroscopy and quantum information science by leveraging structured light fields and ultrafast optics.