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The hole burning spectra of phenol/ammonia (1:3 and 1:4) clusters were measured by a newly developed four-color (UV–near-IR–UV–UV) hole burning spectroscopy, which is a kind of population labeling spectroscopy. From the hole burning spectra, it was found that single species is observed in an n=3 cluster, while three isomers are observed simultaneously for n=4. A possibility was suggested that the reaction efficiency of the hydrogen transfer from the electronically excited phenol/ammonia clusters, which was measured by a comparison with the action spectra of the corresponding cluster, depends on the initial vibronic levels. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

With infrared transient hole-burning spectroscopy we have investigated the influence of OD···X hydrogen bonds on the vibrational line shape of O–D stretch vibrations in acid zeolites. The effect of hydrogen bonding on the line shape depends critically on the type of hydrogen bond. For hydrogen bonding in a rigid structure, the hydrogen bond determines the inhomogeneous linewidth, but the homogeneous linewidth is determined by coupling to a ∼200 cm-1 lattice mode as concluded from the temperature dependence of the dephasing rate. When the hydrogen bond is formed with an adsorbing molecule, the coupling between the high-frequency O–D stretch vibration and the low-frequency OD···X hydrogen-bond stretching mode does determine the homogeneous linewidth. The difference between the two systems can be explained by the different hydrogen-bond potentials. Variation of the adsorbate provides a means of obtaining conclusive information on the coupling mechanism between the high-frequency O–D stretching mode and the low-frequency OD···X hydrogen-bond stretching mode. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Zero field absorption detected magnetic resonance hole burning measurements were performed on photosynthetic reaction centers of the bacteria Rhodobacter sphaeroides R26 and Rhodopseudomonas viridis. Extrapolation to zero microwave power yielded pseudohomogeneous linewidths of 2.0 MHz for Rhodopseudomonas viridis, 1.0 and 0.9 MHz for the protonated forms of Rhodobacter sphaeroides R26 with and without monomer bacteriochlorophyll exchanged, and 0.25 MHz as an upper limit for fully deuterated reaction centers of Rhodobacter sphaeroides R26. The measured linewidths were interpreted as being due to unresolved hyperfine interaction between the nuclear spins and the triplet electron spin, the line shape being determined by spectral diffusion among the nuclei. The difference in linewidths between Rhodobacter sphaeroides R26 and Rhodopseudomonas viridis is then explained by triplet delocalization on the special pair in the former, and localization on one dimer half on the latter. In the fully deuterated sample, four quadrupole satellites were observed in the hole spectra arising from the eight 14N nitrogens in the special pair. The quadrupole parameters seem to be very similar for all nitrogens and were determined to κ=1.25±0.1 MHz and η=0.9±0.1 MHz. [ABSTRACT FROM AUTHOR]

The first paper in this series presented a detailed analysis of the diffraction efficiency of a single holographic grating obtained by spectral hole burning. This paper covers the influence of phase changes which occur during the burning of a single hologram, and the interaction of spectrally adjacent two laser induced gratings. A theoretical description of the holographic efficiencies which takes into account the influence of the relative phases between the two gratings. Experimental results are presented and discussed in terms of the theory. [ABSTRACT FROM AUTHOR]

Doppler-free spectra of two vibronic bands in the A (1B3u)←X (1Ag) transition of the photochemically instable s-tetrazine (H2C2N4) are presented. For the first time saturation spectroscopy is successfully applied to a large polyatomic molecule. Photochemical decomposition of s-tetrazine molecules takes place after excitation and prevents the molecule from returning to the ground state by radiation and nonradiative processes. This represents a particular type of hole burning in the ground state velocity distribution. The elimination of the inhomogeneous Doppler broadening enables us to determine collisionless homogeneous linewidths. For the 0–0 band a value of γ=190 MHz is found whereas the 16a11 band at higher excess energy (ν’16a =256 cm-1) shows a sharper linewidth of γ=140 MHz. No rotational dependence of the linewidth is found in the 0–0 band up to J levels higher than 70. It is argued that internal conversion to the X (1Ag) state is the process responsible for the observed linewidths and that dissociation takes place on the electronic ground state potential surface. [ABSTRACT FROM AUTHOR]

This paper deals with our on-going work on the electronic spectroscopy of tetrapyrrole molecules embedded in cryogenic hosts. Under nanosecond laser excitation of free-base tetrabenzoporphin molecules in a nitrogen matrix at 8 K, increasing laser pulse energy results in essential enhancement of the intensity of one or several vibronic emission lines in the fine-structure fluorescence spectrum. Some characteristics of stimulated radiation are realized in the observed intense monochromatic radiation as a result of a transition from the purely electronic S1 level to a vibrational sublevel of the S0 state, corresponding to the excitation of C-C stretching vibrations of tetrapyrrole methane bridges. We also report on persistent spectral hole-burning effects. Hole and antihole formation analysis gives some insight on the photochemical properties of tetrabenzoporphin in a nitrogen matrix. [ABSTRACT FROM AUTHOR]

A new type of double-resonance spectroscopy of a quantum gas based on interaction-induced frequency modulation of a probe transition has been considered. Interstate interaction of multilevel atoms causes a coherence-dependent collisional shift of the transition between the atomic states |1〉 and |2〉 due to a nonzero population of the state |3〉. Thus, the frequency of the probe transition |1〉−|2〉 experiences oscillations associated with the Rabi oscillations between the states |1〉 and |3〉 under continuous excitation of the drive resonance |1〉−|3〉. Such a dynamic frequency shift leads to a change in the electromagnetic absorption at the probe frequency and, consequently, greatly enhances the sensitivity of double-resonance spectroscopy as compared to traditional 'hole burning', which is solely due to a decrease in the population of the initial state |1〉. In particular, it has been shown that the resonance linewidth is determined by the magnitude of the contact shift and the amplitude of the drive field and does not depend on the static field gradient. The calculated line shape and width agree with the low-temperature electron-nuclear double-resonance spectra of two-dimensional atomic hydrogen. [ABSTRACT FROM AUTHOR]

Abstract: A cascade of two slabs of dissimilar structurally chiral materials can function as a spectral hole filter for normally incident, circularly polarized light, provided (i) both have the same structural handedness and (ii) their constitutive parameters and thickness satisfy two matching conditions. When the total thickness of the cascade is relatively small, a narrow spectral hole is found in the reflection spectrum of co-handed light. Conversely, an ultranarrow spectral hole is found in the transmission spectrum of cross-handed light, when the total thickness of the cascade is relatively large. [Copyright &y& Elsevier]

Abstract: Several different models have been proposed to explain the origin of the complex anti-hole features observed in hole-burned (HB) spectra of excitonically coupled systems such as photosynthetic complexes. This lack of consensus presents a serious constraint on the interpretation of HB spectra and the underlying electronic structures of these systems. To resolve this problem we present results of modeling studies of non-resonant HB spectra taking uncorrelated excitation energy transfer and excitonic interactions into account. Simplified analytical results are compared with Monte Carlo simulations in which excitonic interactions are explicitly taken into account in order to disentangle a number of distinct effects. It is shown that these effects can accurately account for both hole shapes and the broad anti-hole structure observed in excitonically coupled systems. We argue that these models will provide a necessary framework for probing the electronic structure of these systems via HB spectroscopy. [Copyright &y& Elsevier]

Abstract: Optical ultra-short pulse compression and amplification using semiconductor optical amplifier (SOA) is presented. Using pump-probe pulse configuration, we present an SOA model which includes the nonlinear effects such as, spectral hole burning (SHB), carrier heating (CH), two-photon absorption (TPA) and group velocity dispersion (GVD) taking into account gain spectrum effect. Then by adjusting time delay between the pump pulse and probe pulse we use the model for simultaneous compression and amplification of probe pulse. We also analyze the four wave mixing (FWM) signal during pulse compression process. It is shown that dispersive effect of GVD on output probe pulse becomes more important for larger cavity length and probe-pump pulses relative time delays. [Copyright &y& Elsevier]

We numerically and experimentally investigate the high-speed small-signal cross-gain modulation (XGM) characteristics of a quantum-dot (QD) semiconductor optical amplifier (SOA). From a p-doped QD SOA operating at 1.3 μm, high-speed small-signal XGM responses up to 40 GHz are measured from low to high injection currents and improve at high injection currents. In the numerical model, we set up about six hundred coupled rate equations, where the carrier dynamics of QD electron and hole states are considered separately and the enhanced hole occupation due to p-type doping is included. The high-speed small-signal XGM spectra are calculated at various modulation frequencies and pump-probe detunings. We identify how the two separate XGM mechanisms of total carrier density depletion (TCDD) at low injection current and spectral hole burning (SHB) at high injection current affect the high-speed small-signal XGM behavior. From the measured and calculated results, we show that high-speed small-signal XGM responses of QD SOAs can be improved by injecting more carriers to the QD excited states, which enhances high-speed XGM induced by SHB rather than by TCDD. [ABSTRACT FROM AUTHOR]

Abstract: Femtosecond PTHB spectroscopy was expected to demonstrate the existence of distinct s–p absorption subbands originating from the three nondegenerate p-like excited states of hydrated electron in anisotropic solvation cavity. Yet no conclusive experimental evidence either for this subband structure or the reorientation of the cavity on the picosecond time scale has been obtained. It is shown here that rapid reorientation of s–p transition dipole moments in response to small scale motion of water molecules is the likely culprit. The polarized bleach is shown to be too low in amplitude and too short lived to be observed reliably on the sub-picosecond time scale. [Copyright &y& Elsevier]

Wavelength and directional hysteresis due to increasing and decreasing current and temperature have been investigated. Measurements indicate that lasing direction hysterysis associated with changes in injection current can be attributed to the resulting shift in the linear gain peak which is due to the change in device temperature. Enteraction between the linear gain spectrum and the asymmetric nonlinear gain spectrum results in contrasting behavior for increasing and decreasing temperature and current. The phenomena are modeled using a nonlinear time domain model including the carrier density pulsation (CDP), carrier heating (CH) and spectral hole burning (SHB) effects. The numerically reproduced hysteresis loop is in close agreement to the experimental observation. Our work further shows that mode hops to longer wavelength non lasing modes are quicker than those to shorter wavelength lasing modes due to the lack of four wave mixing (FWM) mode coupling in the non-lasing mode. The same model can be used to study the dynamics during switching of lasing directions triggered by other means, such as optical injection. [ABSTRACT FROM AUTHOR]

Abstract: We study the generation of spin squeezing via the hole burning of selected Dicke states out of an atomic coherent state prepared for a collection of N two-level atoms or ions. The atoms or ions of the atomic coherent state are not entangled, but the removal of one or more Dicke states generates entanglement, and spin squeezing occurs for some ranges of the relevant parameters. Spin squeezing in a collection of two-level atoms or ions is of importance for precision spectroscopy. [Copyright &y& Elsevier]

Abstract: Optical Stark spectroscopy of solids has been closely associated with Alexander Kaplyanskii over the last four decades. The field is reviewed here with some emphasis on the use of spectral hole burning and coherent transient techniques to measure linear and quadratic Stark coefficients. Examples are drawn from a wide range of materials including transition metal and rare-earth-doped insulators, color centers, organic molecular solids and semiconductors. Tabulation of data drawn from the literature of the last 50 years is juxtaposed to give some perspective and suggest material, which might benefit from future application of high-resolution spectroscopic techniques. [Copyright &y& Elsevier]

Abstract: The small width of purely electronic zero-phonon lines (ZPL) opens attractive possibilities of their study with the help of Doppler effect (DS—Doppler Spectroscopy). In order to shift the ZPL with 10MHz width to a new position the velocities of the detector relative to the source of the order of tens of meters per second are sufficient. The narrower the line or the spectral hole (its negative image), the more efficient is DS. The DS of the spectral holes shapes and the possibilities of the super-sensitive DS are discussed; the peculiarity of the DS frequency modulation (the perturbations of the internal states of the emitter and absorber are absent) is pointed out. Thus it is interesting to study the interference of the photon “with itself” when the frequency of “its half” is changed by DS. [Copyright &y& Elsevier]

We review recent demonstrations of wide band radio frequency (rf) spectral analyzers based on spectral hole burning technology. The optically carried rf signal can be analyzed with sub-MHz resolution over tens of GHz instantaneous bandwidth. [ABSTRACT FROM AUTHOR]

In order to understand and explain recently reported nonlinear behaviors in semiconductor ring lasers (SRLs) and to further design novel functional devices, a multimode model has been developed for linear and nonlinear interactions between modes in an SRL lasing unidirectionally. The model includes population pulsation, spectral hole burning, carrier healing, and four-wave mixing effects. Heterodyne detection has been used to make high-resolution measurements of the lasing spectra of an SRL in which the individual resonances associated with the coupled eigenvalues can be observed. By fitting these high-resolution spectra to the model, we have extracted a number of key parameters characterizing the coupling mechanisms in the device and the semiconductor gain medium. Using these parameters, the model generates device characteristics in very good agreement with experimental results, which validate its use for future device design and optimization. [ABSTRACT FROM AUTHOR]

We demonstrate implementation of the chirp transform algorithm with photon echoes in an Er3+ :YSO crystal at 1536 nm for application to spectral analysis of RF signals. The principle and features of the technique are presented using a simple picture in the time-frequency plane. Experimental results with low-bandwidth RF signals demonstrate 40-kHz spectral resolution and a time-bandwidth product of 500. Extension to broad-band RF signals is discussed. [ABSTRACT FROM AUTHOR]

Techniques of spectral hole burning and single-molecule spectroscopy have been used to study thin films of polycrystalline terrylene-doped biphenyl at temperatures between 1.7 and 2.2 K. A very wide range of probabilities of photoinduced spectral transitions of terrylene molecules are indicated by the strong non-exponentiality of non-photochemical hole burning processes and observation of some extremely stable single-molecule lines. Broad distribution of single-molecule linewidths as well as obvious disagreement between their average value and the corresponding holewidth also demonstrate a large variety of spectral behaviour of terrylene impurity molecules. We attribute these effects to spatial variations of local environment of terrylene molecules in an incommensurate matrix of biphenyl. [Copyright &y& Elsevier]

We have measured the hole spectra in YSZ:Pr3+ and YSZ:Eu3+ with various Y2O3 concentrations at low temperature. The temperature dependence of the hole width which obtained from the hole spectra in YSZ:Pr3+ and YSZ:Eu3+ was similar to that for disordered materials. However, the Y2O3 concentration dependence of the hole width in YSZ:Pr3+ was contrary to that for YSZ:Eu3+ at low temperature. The hole width was the widest in the case of YSZ:Pr3+ at 10 mol% Y2O3. On the contrary, it was the narrowest in the case of YSZ:Eu3+ at the same concentration of Y2O3. It was found that there are two states in YSZ, in which the degree of ordered differs from each other. Additionally, the Y2O3 concentration dependence of the hole width at low temperature has reflected the ionic conductivity of YSZ at high temperature. It is suggested that the ordering of local structure is responsible for the ionic conduction in YSZ. [Copyright &y& Elsevier]

Partial deuteration of NaMgAl(oxalate)3 · 9H2O:Cr(III) (0.5%) increases the quantum efficiency for persistent spectral hole-burning in the R1-line by three orders of magnitude. A 50% deuterated crystal shows an impressive initial hole-burning efficiency of ≈0.1% and sharp anti-holes are observed in the range of ±15 GHz. A decrease of the quantum efficiency upon deuteration has often been reported in the literature and this has been rationalized on the basis of the lower tunnelling probability of the deuteron in the double well potential of hydrogen bonds. In contrast, the present findings of a sensational increase can be rationalized by a hole-burning mechanism based on 180° flip motions of the lattice water molecules around their pseudo C2 axes. Considering the spin-flip nature of the electronic excitation this is an extraordinary finding. The deuteration effect may be used to design high-efficiency hole-burning materials for optical storage at liquid nitrogen temperatures. [Copyright &y& Elsevier]

A few examples of progress of studies and applications of purely electronic zero-phonon line are considered: new experimental values of the narrowest line, femtosecond time-and-space-domain holography and the Taffoli gate by means of it; promises of quantum computing compared to what already done in holography. [Copyright &y& Elsevier]

We present optical spectroscopy measurements of a supramolecular assembly C60–H2TPP in poly-vinylbutyral (PVB) and compare its photophysical properties to separated C60 and H2TPP in PVB. Optical absorption and emission from the supramolecular assembly mainly appears as resulting from a superposition of the respective properties of the fullerene and porphyrin moieties. However, emission features unique to the supramolecule assembly are found and reported. Spectral hole-burning properties of the supramolecule are similar to those observed for separated C60 and H2TPP. This demonstrates that the phototautomerisation induced in the porphyrin moiety and thought to be responsible for the formation of the spectral hole is largely unaffected by the presence of the fullerene. [Copyright &y& Elsevier]

Reduction of D4h symmetry of the porphyrin dianion in such a way that the axes passing the pyrrolic nitrogens are made inequivalent leads to distinct structures of prototropic tautomers of the respective diprotonated (neutral) compound. The accompanying difference in S1 energies between the two states is a highly desirable property of a hole-burning (HB) system with minimum overlap between the educt and product absorption. Several porphyrins carrying electron-donating alkyl and electron-withdrawing Br substituents at pyrrolic β positions were doped in a poly(vinyl butyral) film and utilised as HB materials at 8 K. The band maxima, inhomogeneous widths, the Debye–Waller factors (DWF) and the HB efficiencies were determined for both tautomeric forms. The substitution at pyrrolic β positions is a delicate way of perturbing the π electron system as compared to breaking the conjugation by reduction of one of the pyrroles in chlorin. In chlorin the quantum yield, the DWF and the thermal stability of the photoproduct are unfavourable for HB as a result of too strong axial inequivalence. In the red shifted tautomers of 2,3,12,13-tetraethylporphine (TEP) and 7-Br-TEP the advantages of symmetric molecules such as octaethylporphine are retained. [Copyright &y& Elsevier]

We report on the spectroscopic and hole burning properties of free-base naphtophthalocyanine with and without 1-chloranthracene in polymer host. These materials exhibit a strong 0–0 absorption band in the region 800 nm matching the wavelength range of most semiconductor and Ti:Sapphire lasers. The materials studied feature two persistent hole burning photochemical mechanisms, i.e. one-photon proton tautomerization, and two-photon-gated hole burning likely due to donor–acceptor electron transfer. The last mechanism includes the long living intermediate state. The hole width at 1.5 K is about 300–400 MHz depending on the hole burning conditions, while the inhomogeneous width is about 107 MHz. Holographic storage is an important potential application of these materials. We demonstrated 10 plane wave holograms angularly multiplexed at one frequency channel in a spectral hole burning medium. It was shown that the M/# is still a valid system metric and the measured M/# in one frequency channel is about 0.01. [Copyright &y& Elsevier]

The polydispersive dielectric response of a lanthanum-modified lead zirconate titanate relaxor ferroelectric was studied using nonresonant hole burning (NHB) spectroscopy. The dynamic heterogeneity of this material was evidenced by the fact that it was possible to burn frequency-dependent spectral holes. The maximum position of the spectral holes depended on the square root of the pump frequency Ω. The refilling of the spectral holes was monitored subsequent to excitation using various pump frequencies. The refilling data could be collapsed onto a master curve by re-scaling them, again, using Ω−0.5 as scaling factor. The refilling time was found to be much longer than the time scale addressed most by the pump process. This behavior underscores the importance of domain wall motions for the dielectric relaxation process. [Copyright &y& Elsevier]

Femtosecond spectral hole burning experiments were performed on InAs/GaAs quantum dots to investigate the influence of high excitation intensities. The observation of additional spectral holes, as well as distinct absorption line broadening are both attributed to two-photon absorption processes. These spectral holes can be unambiguously assigned to degenerate two-photon biexciton creation, whereas the absorption line broadening is a direct result of Coulomb renormalization, initiated by carriers created through two-photon absorption in the surrounding GaAs crystal matrix and the InAs wetting layer. [ABSTRACT FROM AUTHOR]

Zero-phonon hole (ZPH) profiles and hole spectra that span about eight decades of burn fluence are reported for Al-phthalocyanine tetrasulphonate in hyperquenched glassy water (HGW) films at 5.0 K. The profiles of unsaturated zero-phonon holes (low burn fluence stage) are more sharply tipped than a Lorentzian. It is shown that the non-Lorentzian behavior is a natural consequence of the interplay between the three distributions that govern the dispersive kinetics of nonphotochemical hole growth. They are denoted by λ, α, and ω, where λ is the tunnel parameter associated with nonphotochemical hole burning (NPHB) and α is the angle between the transition dipole and the laser polarization. The ω distribution stems from off-resonant absorption of the zero-phonon line (ZPL). The single site absorption spectrum used in the calculations included the ZPL and the phonon sideband. The contribution of a distribution of homogeneous ZPL widths to the non-Lorentzian behavior was assessed and found to be negligible compared to that of the above distributions. The burn fluence dependence of the hole spectra, which include the ZPH, phonon sideband, and antihole structures, leads to new insights on the mechanism of NPHB, ones that necessitate modification of the Shu-Small mechanism [L. Shu and G. J. Small, J. Opt. Soc. Am. B 9, 724 (1992)]. Although that mechanism recognizes the importance of coupling between the intrinsic and extrinsic two-level systems (TLS[sub int],TLS[sub ext]) of the chromophore/glass system and diffusion of excess free volume triggered by optical excitation, it does not adequately account for the effects of multiple excitations of redshifted (relative to the burn frequency ω[sub B]) preburn and antihole sites. The results show that multiple excitations ultimately lead to the entire antihole being blueshifted. A "second channel" of hole burning becomes apparent at sufficiently high burn fluences. A model for t... [ABSTRACT FROM AUTHOR]