In this work, we analyse the use of a micro-machined deformable membrane mirror (MMDM) to shape femtosecond
pulses. We present the Spectral-Phase-Influence-Matrix constructed by an inversion method. Spectral-Phase-Influence-
Matrix represents a novel and direct method to estimates the Spectral Phase design from a given actuator voltage settings
in a single step. Numerical and experimental results are presented.
Photoluminescence (PL) belongs to the group of non-destructive characterization techniques, which consists basically in causing to impact light in a region of the material under study. Then, the material absorbs part of the energy of the incident light and, as a consequence, emits light. This technique is widely employed in different areas of the Industry and Basic Research; for example, in Medicine, Chemistry, Biology, Physics and in several areas of Engineering. As excitation source it can be used lamps, lasers and even solar light.
On the other hand, there are processes that can occur to extremely short time scales. In this case new techniques have been developed. Among them, we can mention Time Resolved Photoluminescence. In this technique ultra-short laser pulses are employed which have a temporal width from a few nanoseconds (x10-9 sec) until femtoseconds (x10-15 sec). The use of pulsed lasers has served for the development of new methods of investigation and technologies, as has been the case of Femto-Chemistry, new Surgery methods in Medicine, Micro- and Nano- machining of materials, etc. In our case, we utilize Photoluminescence and the Time Resolved Photoluminescence for the characterization of semiconductors materials that have potential applications in Optoelectronics.
In this work, we present results on the characterization of ultrashort laser pulses in the range of tens of femtoseconds by three techniques: autocorrelation, spectral analysis and optical interference. Pulses are generated by a Ti-Sapphire (Ti:Sa) laser pumped by a solid state laser. The temporal width of the pulse (FWHM) was measured at different wavelengths from 730 to 820 nm. At the same wavelength, we obtained different values depending on the characterization technique used. We discuss those results and the theoretical models used in each case. For autocorrelation and spectral analysis, we assume an almost-Gaussian pulse to calculate the pulse width. The mathematical model employed allowed us to estimate deviations from this approximation. The experimental results obtained by interferometry allowed us to control the spatial and temporal distance between pulses. The spectral properties of almost-Gaussian functions are considered and applied to characterize to a second-order approximation in the expansion of the coefficients the pulses. Specifically, adding small amounts of odd-order Hermite-Gauss to a Gaussian induces a second-order increase in the time-bandwidth product, while the increase in the time-bandwidth product from adding even-order Hermite-Gaussian is higher-order and hence smaller. We compare the almost-Gaussian functions with femtosecond temporal width pulses data obtained for the Ti:Sa laser.
CdTe ultra-thin quantum wells (UTQWs) within ZnTe barriers were grown by pulsed beam epitaxy (PBE) on GaAs(001) substrates. In-situ reflection high energy electron diffraction (RHEED) patterns and real-time spot intensity measurements indicated a high structural quality of the QWs. Low temperature photoluminescence (PL) experiments indicated a clear influence of the growth temperature on the structural properties of the samples. The 2 monolayer (ML) thick UTQW grown at Ts = 270°C exhibited an intense and sharp peak at 2.26 eV whereas the 4 ML thick UTQW (Ts = 290°C) presented an intense peak at 2.13 eV and a weak one around 2.04 eV. This behavior is discussed in terms of Cd re-evaporation at the higher Ts.
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.