We demonstrated that ultrafast azimuth rotation of linearly polarized beam by use of a chirped optical pulse pair, and the rotational frequency of sub-THz was realized.
Subsequently to the previous generation of ultrashort and ultra-broadband optical-vortex (OV) pulses (pulse energy: several tens of μJ) in few-cycle regime, we performed the generation of axisymmetrically polarized pulses with spatial complex amplitude modulation, which is suitable for a broadband spectrum. The generation system employs the combination of spatial light modulators in the 4-f configuration and a space variant wave plate as a common path interferometer. The spatial light modulators in the 4-f configuration offer the spatial dispersion compensation with respect to wavelength; in addition, the common path interferometer provides the stability to perturbation. We experimentally demonstrated the generation of various axisymmetrically polarized pulses by applying modulations of fundamental and higher-order Laguerre-Gauss modes with high purity. The experimental results show that we are able to generate arbitral axisymmetrically polarized pulses with spatial complex amplitude modulation.
Single angular momentum (OAM) mode emissions from a vertical cavity surface emitting laser (VCSEL) were
demonstrated by an external optical feedback using computer generated holograms, which are optimized on the OAM
modal gain of the free-running VCSEL. Side-mode suppression ratio of more than 23 dB was achieved for the OAM
modes with l = ±1.
A new method for the ultrafast rotation of ring-shaped optical lattices based on frequency-chirping of optical pulses
was demonstrated in THz regime, which is three orders of magnitude faster than those by the conventional methods. Our
optical lattice generator with a spatial light modulator is robust thanks to the 4-f configuration and enables us to flexibly
control their rotational symmetry. The generated ultrafast-rotating ring-shaped optical lattices with a rotational frequency
of 0.59 THz were successfully boosted from 5 μJ up to 125 μJ by using a home-built 4-pass Ti:sapphire amplifier without
any limitation by optical damage to the spatial light modulator.
Subsequently to the previous generation of ultrashort and ultra-broadband optical-vortex (OV) pulses (pulse energy: several tens of μJ) in few-cycle regime, we demonstrate high-power OV pulse generation with topological charge flexibility by employing a 4-f OV converter and pre- and main-amplifications. Our configuration overcomes the low-throughput drawback of the vortex converter, simultaneously compensating for the angular dispersion. It also gives flexibility of OAMor topological-charge control. Thus, we succeed in generation of mJ-class ultra-broadband OV pulses (∼790-∼820 nm) with a programmably-controlled topological charge. Moreover, we experimentally exhibit a high-precision method for measuring frequency-resolved OAM spectrum of femtosecond ultra-broadband OV pulses on the basis of electric-field reconstruction in the spatial domain. In addition, we present the generation of ultrashort pulses with axially-symmetric polarization by coherent beam combining of OVs.
Due to the recent progress of material science, quasi-one-dimensional (1D) materials provide an opportunity for investigating the influence of topology and dimensionality on their optical and electrical properties. In this study, we report the phase transition properties of such quasi-1D compounds by utilizing an ultrafast optical spectroscopy. Photoexcited nonequilibrium carrier dynamics yield characteristic features around the phase transition temperatures. We also discuss the toplogical effects on the phase coherence of correlated carriers by using both polarization and excitation energy dependences of the transient signals and their spatial characteristics.
We perform degenerate four-wave-mixing (FWM) studies of GaN excitons especially for an understanding of the strain-fields in the heteroepitaxial films. The shifts of exciton energies and their beating oscillation variations highlight the biaxial strain, allowing for a precise determination of the strain parameters.
The uniaxial strain field can be characterized by the polarization dependence of FWM, which shows distinct polarizations and energy variations depending on the sample and its position. The minimum changes of the polarized FWM intensity and exchange energy splittings correspond to a uniaxial strain of 5.0 × 10-5, which currently gives a lower resolution limit of this technique and is comparable with that of conventional X-ray diffraction.
In the time-evolutions, we investigate the strain effects on the phase of the quantum beats (QBs), giving insight into the excitons interactions. By using time-resolved FWM, difference between two-types of exciton transitions is identified. In addition, coherent manipulations of QBs are successfully realized in the FWM with a Michelson interferometer.
We report photoluminescence (PL) studies of zero-dimensional excitonic confinement in InAs/GaAs self-assembled quantum dots (SAQDs) fabricated by Stranski-Krastanow growth. A low- temperature near-field optical microscope is employed to identify individual PL peaks due to single SAQDs. Highly spatial and spectral evaluation of each PL peak identify the Zeeman spin splitting with the magnetic field up to 10 T. The comparison of different confinement structures was also discussed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.