Optical Hole Burning Research Articles

Samarium doped alkaline earth halide thin films as spectrally selective materials for hole burning?

Abstract Optical hole burning, a potential technique for spectrally selective recording, was demonstrated in Sm-doped MBE-grown thin films of CaF2/Si(111). The inhomogeneous broadening of the corresponding Sm2+ 5d(T1u) ↞ 4f(7F0, A1g) transition (690 nm) was investigated as a function of substrate temperature and film thickness. The MBE apparatus is briefly described as well as the thin film growth procedure.

Rotational tunneling dynamics of methyl groups inn-alkane host lattices: An optical investigation of the internal and external isotope effect

We exploited the slow relaxation of methyl group rotational tunneling states to perform optical hole burning inn-alkane crystals. The dye probe used was dimethyl-s-tetrazine and its perdeuterated derivative. We investigatedn-octane, perdeuteratedn-octane andn-hexane as host crystals. By comparing the experimentally observed hole-antihole splitting of the protonated and perdeuterated dye probe, all parameters, i.e. the tunneling splitting in the ground-and in the electronically excited state as well as the respective heights of the potential can be determined, assuming a threefold rotational symmetry axis. We found that matrix deuteration has a severe influence on the potential heights, which increase by a factor of two. With these parameters determined, many features of the complex relaxation behavior of the tunneling states can be qualitatively understood: We found Raman-type conversion processes inn-octane-h 18, Orbach-type processes inn-octane-d 18 and inn-hexane we found, in addition, a relaxation regime governed by a Direct process. The experimental activation energies as well as the cross-over temperatures are in satisfying agreement with current theories.

Time-resolved ultranarrow optical hole burning of a crystalline solid: Y_2O_3:Eu^3+

Optical hole burning is used to study optical dephasing of the 7F0 ⇒ 5D0 transition in samples of Y2O3:Eu3+ grown by both flame fusion and laser-heated pedestal growth. The samples exhibited a wide variation in their low-temperature hole widths, and the measured hole linewidths were in reasonable agreement with homogeneous linewidths obtained from values of T2 that were determined with two-pulse photon echoes. The sample that had the longest value of T2 (510 μs) from the echo measurements gave a hole width of 3.5 kHz. This is believed to be the narrowest spectral feature observed directly in the frequency domain for a solid. Other samples produced wider holes that were not correlated with the Eu3+ impurity concentrations. Time-resolved hole burning in one of the samples showed a slow and continuous broadening of the spectral hole from 130 kHz at 3 ms to 900 kHz at 10 s after hole burning. It is suggested that the additional broadening is associated with some form of disorder modes in this ordered crystalline solid.

Measurement of the size dependent hole spectrum in CdSe quantum dots.

We combine a new synthesis with transient optical hole burning to observe and assign the size evolution (19 to 115 \AA{} diameter, \ensuremath{\sigma}5%) of a series of excited states in CdSe quantum dots. We observe an avoided crossing around the spin orbit energy in the hole spectra for \ensuremath{\sim}65 \AA{} dots, indicating the importance of valence band complexities in the description of the excited states. Comparsion with dc Stark data shows that bleach spectra are consistent with localized carrier induced electric fields.

Long-time spectral diffusion in LaF 3:Pr 3+

Time resolve optical hole burning is used to study spectral diffusion of the 3 H 4⇔ 1 D 2 transition in a LaF 3:Pr 3+ in a time scale of millisecond to seconds. The evolution of the hole depended strongly on the magnitude of an applied magnetic field. The amount of spectral diffusion observed was larger thanwhat could be explained through F-Pr dipolar interactions.

Surface effects on the optical properties of cadmium selenide quantum dots

Cadmium selenide quantum dots were synthetized with different functional groups attached to their surfaces. The effect of surface chemistry on the optical properties was determined through optical hole-burning and luminescence measurements. Nanosecond hole burning problem ground-state recovery due to recombination at trap states, and the results indicate that nanocrystallites with better surface passivation and stronger bonds to terminating ligands have longer ground-state recovery times. Better surface passivation and stronger bond strength were also correlated with increased luminescence intensity, which shows the relative amount of radiative recombination

Size dependent optical spectroscopy of II?VI semiconductor nanocrystallites (quantum dots)

We use low temperature (10K) optical hole-burning and fluorescence line narrowing spectroscopy to investigate the electronic properties of CdSe nanocrystallites (quantum dots) as a function of crystallite diameter (20–80A). We discuss how the homogeneous linewidth of the HOMO-LUMO transition, the energy shift between the absorbing and emitting state, and the LO phonon frequency vary with nanocrystallite size.

Dynamics of adsorbed molecules in zeolites

Dye molecules adsorbed or embedded in the cages of a microporous zeolite have unique degrees of freedom which are not available to chromophores in e.g. molecular crystals or glasses. We have used low temperature optical spectroscopy and spectral hole burning to study the dynamics of a selected system, namely thionine molecules in a faujasite structure. The spectral properties depend strongly on the water content of the faujasite. Thionine in a hydrated sample shows considerable electron-phonon coupling comparable to the behaviour in a glassy matrix. In a dehydrated sample there exist two stable thionine conformations which can interconvert at low temperatures through ground state as well as excited state reactions. This reversible photocycle explains the appearance of antiholes at the burning wavelength. The electron-phonon coupling in the dehydrated sample is weak, similar to the characteristics of adsorbate/substrate systems.

Energy transfer in the core pigments of phycobilisomes from Mastigocladus laminosus as studied by temperature-dependent hole burning

Persistent optical hole burning has been performed in the allophycocyanin band of phycobilisomes of Mastigocladus laminosus. The homogeneous transition line width has been obtained by a careful analysis of the hole-burning data. The dependence of the line width on temperature has been measured in the range 1.5-4.2 K. A lifetime-limited value of 1.08 A 0.21 GHz is obtained as a result of linear back extrapolation to T = 0 K. It corresponds to an energy transfer time of 147 f IS ps from allophycocyanin to the terminal emitters of the phycobilisome core.

Dynamics in a low-temperature glass: Fast generation and detection of optical holes

High-resolution, fast optical hole-burning results are reported for the amorphous system cresyl violet in ethanol glass at 1.3 K. Holes are burned and detected using a novel technique which allows precise detection of narrow (∼0.03 cm−1 ), shallow (∼1%) holes 10 μs to 50 ms after their generation. The technique is described in detail along with careful tests demonstrating the validity of its results. The hole width is observed to increase linearly with time when plotted against log time. Using the four time correlation function description of optical hole burning, the time-dependent increase in hole width (spectral diffusion) is shown to arise from a broad distribution of fluctuation rates in the glass with the probability of having a fluctuation at rate R proportional to 1/R. The 10 μs to 50 ms data is combined with hole-width data spanning the range 100 ms to 10 000 s and with two-pulse picosecond photon echo data. The two-pulse photon echo linewidth is calculated by extrapolating the fluctuation rate distribution obtained from the hole-width data to short times. The results are in excellent agreement with experimental echo results. The combined data from the two sets of hole-burning experiments provides a detailed description of the glass dynamics over nine decades of time, 10 000 s to 10 μs. Together with the two-pulse photon echo results, the data provide information on the glass dynamical behavior over seven decades faster in time as well. The net result is a description of the dynamics in low-temperature ethanol glass on time scales spanning 16 decades.

Optical hole burning and spectral diffusion in ruby.

Frequency-domain optical hole burning of the ${\mathit{R}}_{1}$ line ${[}^{4}$${\mathit{A}}_{2}$(-1/2)\ensuremath{\leftrightarrows}E\ifmmode\bar\else\textasciimacron\fi{}(-1/2) transition] in dilute ruby is studied at 2 K and with a field of 3.6 kG applied along the c axis. A pump-probe (PP) technique is used with precise probe-frequency shifting obtained by an acousto-optic modulator. For sufficiently short PP pulses (50 \ensuremath{\mu}s), two holes (narrow and wide) are observed. The narrow (\ensuremath{\sim}20 kHz half width at half maximum at low power) hole-width dependence on Rabi frequency approximately agrees with that inferred from free-induction-decay measurements. For the present concentration (0.0034 wt. % ${\mathrm{Cr}}_{2}$${\mathrm{O}}_{3}$) and field, the narrow hole width is determined by fluctuating fields produced by Cr-Cr spin flips [A. Szabo, T. Muramoto, and R. Kaarli, Phys. Rev. B 42, 7769 (1990)]. When the PP delay time is varied, the amplitude of the narrow hole decays with a 1/e time constant of \ensuremath{\sim}300 \ensuremath{\mu}s compared to the E\ifmmode\bar\else\textasciimacron\fi{} fluorescence lifetime of 4 ms. The wide hole (\ensuremath{\sim}500 kHz half width at half maximum) is due to Al-Cr superhyperfine interactions and is created by a spectral diffusion mechanism driven by Al-spin flipping in the host lattice.

Spectral hole burning of photosynthetic antenna of blue-green algae

Photosystem II core antenna of blue-green algae Synechococcus isolated in gel was studied by optical hole burning spectroscopy at 4·2 K. Persistent holes were burned into fluorescence spectra throughout the region 680–696 nm. The hole width extrapolated to zero burning fluence yielded a value 1·0±0·2 cm−1. A theoretical interpretation of the hole profile in fluorescence is presented. The dependence of saturated hole depth on burning wavelength is related to inhomogeneous site distribution function.

Probing low temperature glass dynamics by fast generation and detection of optical holes

High resolution, fast optical hole burning results are reported for the amorphous system cresyl violet in ethanol glass at 1.3 K. Holes are burned and detected using a novel technique which allows precise detection of narrow (≈ 0.03 cm −1), shallow (≈ 1%) holes 10 μ to 50 ms after their generation. The hole width is observed to change linearly when plotted against log time. Using a four point correlation model of optical hole burning, this spectral diffusion is shown to arise from a 1/ R distribution of fluctuation rates. The distribution extrapolates to the value of the two pulse photon echo linewidth measured on the same system.

Methyl group tunneling in molecular solids at low temperatures: A study via optical holeburning of the electronic state dependence and the relaxation dynamics

We report a new approach to study rotational tunneling in condensed phases using high resolution spectral holeburning as line narrowing technique. The method is demonstrated in mixed crystals of di-methyl-s-tetrazine in durene and allows to determine directly the difference of tunneling splitting in different electronic states. It also opens a way to measure relaxation processes between tunneling levels (spin conversion) over large temperature ranges and time scales.

Electronic structure and photoexcited-carrier dynamics in nanometer-size CdSe clusters

We use transient optical hole burning and photoluminescence to investigate the static and dynamic electronic properties of 32-\AA{} CdSe quantum dots. We observe a number of discrete electronic transitions, resolve LO-phonon progressions, and obtain homogeneous linewidths and electron--LO-phonon couplings. We find that the band-gap luminescence is not from the exciton state, but from a surface trapped state. Rapid (\ensuremath{\sim}160 fs) trapping into these surface states results in long-lived (\ensuremath{\sim}10--100 ns) bleach and induced-absorption features in pump-probe experiments.

Solvation shell effects and spectral diffusion: Photon echo and optical hole burning experiments on ionic dyes in ethanol glass

Results of picosecond photon echo and optical hole burning experiments are reported for four ionic dyes in ethanol glass. At low temperatures, the dephasing times deduced from the hole widths are as much as nine times shorter than those measured by the two-pulse echo because of the effect of spectral diffusion. The temperature dependences found are of the form aTα+b exp (−ΔE/kT) due to glass two level system dynamics (T<4 K) and a process that activates exponentially at higher temperatures, possibly from a pseudolocal mode or glass optical phonon. Comparing the ratios of echo to hole burning measured dephasing times for the four dyes suggests that the dephasing is influenced by the existence of distinct local ethanol solvation shells in addition to the dynamics of the bulk solvent. A theoretical description of solvent shell effects is achieved through the use of a two spatial domain model of the glass dynamics. Calculations of dynamic perturbations from distinct solvation shell and bulk solvent regions show that the observed differences between the dyes’ dephasing ratios can be explained if the ionic chromophores alter glass dynamics locally.

Spectral hole burning of model photosynthetic systems

Basic problems in the primary processes of photosynthesis, interactions between pigments, proteins and quinones, as well as processes of energy transfer and electron transport in the primary events were studied using low temperature optical spectroscopy (hole burning technique). The obtained results (homogeneous widths of optical transitions and hole burning kinetics) were correlated on both model and in vivo photosynthetic systems.

Optical holeburning and double resonance spectroscopy of Ho3+ In CaF2

Abstract The charge compensated trigonal centre of Ho3+ in CaF2 has been investigated using optical holeburning. Optical-MW and Zeeman techniques. The data have been utilised to determine nuclear hyperfine and quadrupole parameters and nuclear gyromagnetic ratios for the electronic states involved.

Tunneling dynamics of delocalized protons in hydrogen bonds at low temperatures

Abstract High-resolution optical holeburning is used to characterize the tunneling potential of delocalized protons in benzoic acid dimers coupled to a dye molecule. The effect of pressure on the system is measured and the relaxation rates between the tunneling levels are determined from the homogeneous linewidths.

Optical Hole Burning and Thermal Irreversibility of Non‐Ergodic Systems: Polymers, Proteins, Glasses

AbstractA spectral hole is used to probe configurational dynamics of non‐ergodic systems far below the glass transition temperature.