Intra Cavity Research Articles

Design of an Optimized Helical Antenna for Intra Cavity Hyperthermia Applications

In this paper an optimized helical antenna is proposed for heating ablation (Hyperthermia) of uterus, ovarian and colon cancers. This antenna is designed in such a way that can be easily insert into the intra cavities, due to its size and flexible shape. Various characteristics of the proposed helical applicator are investigated and optimized for best created specific absorption rate (SAR). After optimizations, the special proposed helical antenna is able to process the maximum symmetry radiation beams and this is an important feature because the cavity which the antenna is located must have capability to heat same in all directions. Finally, measured results of the constructed applicator are presented by the accuracy of simulated results.

Comparison of single-side and double-side pumping of membrane external-cavity surface-emitting lasers.

We studied and compared single-side pumping (SSP) and double-side pumping (DSP) of a semiconductor membrane external-cavity surface-emitting laser (MECSEL). The MECSEL-active region was based on an AlGaAs quantum well structure embedded between two silicon carbide (SiC) wafer pieces that were used as transparent intra-cavity (IC) heat spreaders creating a symmetrical cooling environment. The gain structure targeted emission at 780 nm, a wavelength region that is important for many applications, and where the development of high-brightness high-power laser sources is gaining more momentum. By DSP at 20°C heat sink temperature, we could reduce the laser threshold from 0.79 to 0.69 W of absorbed pump power, while the maximum output power was increased from 3.13 to 3.22 W. The differential efficiency was improved from 31.9% to 34.4%, which represents a record value for SiC-cooled vertically emitting semiconductor lasers. The improvements are enabled by a reduced thermal resistance of the gain element by 9% compared to SSP. The beam quality was measured to be M2<1.09. Finally, we demonstrate a maximum tuning range from 767 to 811 nm. This wavelength range was not addressed by any MECSEL or vertical external-cavity surface-emitting laser device before and extends the available wavelengths for semiconductor based high-quality beam and high-power laser sources to a wavelength window relevant for quantum technology, spectroscopy, or medicine.

New Perspectives in Monitoring the Flame Synthesis of Iron Oxide Nanoparticles: Addressing Solid and Gas-Phase Diagnostics Challenges

ABSTRACTSeveral techniques for in-situ monitoring and characterization of flame synthesized nanoparticles are described with the goal of gaining further insight into the mechanisms governing nanoparticle (NP) formation in flame reactors. These include: a combined particle mass spectrometer - quartz crystal microbalance apparatus (PMS-QCM); The Light Induced Detuning –Quartz Crystal Microbalance (LID-QCM) method; Application of Intra Cavity Laser Absorption Spectroscopy (ICLAS) for monitoring gas phase intermediates in a particle laden environment.

Intra–cavity generation of Bessel–like beams with longitudinally dependent cone angles

We report on two resonator systems for producing Bessel-like beams with longitudinally dependent cone angles (LDBLBs). Such beams have extended propagation distances as compared to conventional Bessel-Gauss beams, with a far field pattern that is also Bessel-like in structure (i.e. not an annular ring). The first resonator system is based on a lens doublet with spherical aberration, while the second resonator system makes use of intra-cavity axicons and lens. In both cases we show that the LDBLB is the lowest loss fundamental mode of the cavity, and show theoretically the extended propagation distance expected from such beams.

Intra–cavity flat–top beam generation

We present the analytical and numerical analyses of two new resonator systems for generating flat-top-like beams. Both approaches lead to closed form expressions for the required cavity optics, but differ substantially in the design technique, with the first based on reverse propagation of a flattened Gaussian beam, and the second a metamorphosis of a Gaussian into a flat-top beam. We show that both have good convergence properties, and result in the desired stable mode.

Quantitative wideband spectroscopy with kilometric absorption paths

Combining Intra Cavity Laser Absorption and Time Resolved Fourier transform spectro-scopies (ICLAS-TRFTS) brings original advantages that are derived from the ability to obtain consistent series of Fourier spectra recorded according to a well-defined time sequence on the same accurate wavenumber scale. These advantages, mainly centred on the possibility to perform quantitative measurements are discussed and evaluated. Accurate determination of line positions and intensities of ultra weak transitions previously hardly measurable becomes possible. Ultimate limits are estimated for the present experiment in the neqr infrared range for H2O.

New spectroscopic methods for environmental measurement and monitoring

AbstractThe ability to monitor a broad range of chemical species in the atmosphere, geosphere, and hydrosphere is a key technology for addressing global environmental issues. This report surveys several high sensitivity spectroscopic techniques for this purpose, including Frequency‐Modulation‐Enhanced Remote Sensing, Intra Cavity Laser Absorption Spectroscopy, Cavity Ring Down Spectroscopy, and Raman Spectroscopy.

Multi-siting and mode locking in a Yb3+:CS-FAP laser

A Yb3+:CS-FAP (Yb3+:Ca4Sr(PO4)3F) laser has been actively mode locked to generate pulses as short as 35 ps, which were far from transform limited. Intra cavity pulse compression failed to realise the femtosecond pulse generation potential of this relatively broad bandwidth (∼ 10 nm) and efficient laser material. Site-selective excitation techniques were employed to demonstrate an excitation wavelength-dependent laser emission. This spectral inhomogeneity arises from the disorder on the metal host site which is due to random Ca and Sr occupation. Such a characteristic most likely prohibited ultrashort pulse generation with this sample.

Er:Ca5(PO4)3F saturable-absorber Q switch for the Er:glass laser at 1.53 μm

Passive Q switching of an Er:phosphate glass laser using Er:Ca5(PO4)3F (Er:FAP) as a saturable absorber intracavity (IC) load is described for the first time. Q-switched output was obtained consisting of a 6-mJ single pulse of 83 ns full width at half maximum, with a 20% efficiency relative to the corresponding free-running output in the absence of the IC Er:FAP load.