Nonlinear loss characterization of continuous wave guiding in silicon wire waveguides

2021 ◽  
Author(s):  
Masatoshi TOKUSHIMA ◽  
Jun Ushida ◽  
Takahiro Nakamura
Keyword(s):  
Continuous Wave ◽  
Short Pulse ◽  
Propagation Loss ◽  
Photon Absorption ◽  
Light Sources ◽  
Free Carrier Absorption ◽  
Silicon Waveguides ◽  
Nonlinear Loss ◽  
Parameter Values

Abstract Accurate propagation loss characterization of silicon waveguides is increasingly demanded for silicon-photonics-(Si-Ph) applications with high-power continuous-wave-(CW) light sources. We report on nonlinear loss parameters of silicon wire waveguides for 1.31-μm-wavelength CW light extracted from transmission data measured for different lengths and polarizations. Such parameters were, so far, unavailable, although they are required for accurately modeling Si-Ph optical circuits. More-than-ten-times enhancement of two-photon absorption from prior results for short pulse light was observed at power densities ranging up to 4.7×1011 W/m2 while free carrier absorption was suppressed. We estimate the nonlinear loss of the waveguide using the parameter values obtained

TUNABLE ASYMMETRIC FANO LINESHAPES IN SILICON-BASED MICRORING RESONATORS WITH FEEDBACK

2011 ◽  
Vol 20 (03) ◽  
pp. 357-366 ◽  
Author(s):  
SANTHAD PITAKWONGSAPORN ◽  
SURASAK CHIANGGA
Keyword(s):  
Continuous Wave ◽  
Operating Regime ◽  
Free Carrier ◽  
Photon Absorption ◽  
Microring Resonators ◽  
Free Carrier Absorption ◽  
Coupling Coefficients ◽  
Linear Absorption ◽  
Carrier Absorption ◽  
Silicon Based

We theoretically examine the Fano lineshapes of silicon-based compound microring resonators consisting of a single resonator channel dropping filter linked to a loop as a feedback structure. All possible optical effects for the continuous-wave operating regime, such as linear absorption or scattering, two-photon absorption, free-carrier absorption and dispersion, thermo-optics, are simultaneously considered. We show that sharp Fano resonances can be tuned by variation in the coupling coefficients, length of feedback loop, effective free carrier lifetime and the temperature inside the device. Tunable Fano lineshapes open up opportunities for applications in sensing, computing, and communications.

scholarly journals Computational Laser Spectroscopy in a Biological Tissue

2010 ◽  
Vol 2010 ◽  
pp. 1-9 ◽  
Author(s):  
M. Gantri ◽  
H. Trabelsi ◽  
E. Sediki ◽  
R. Ben Salah
Keyword(s):  
Biological Tissue ◽  
Near Infrared ◽  
Continuous Wave ◽  
Light Transmission ◽  
Short Pulse ◽  
Control Volume ◽  
External Source ◽  
Time Dependent ◽  
Infrared Light ◽  
Light Sources

We present a numerical spectroscopic study of visible and infrared laser radiation in a biological tissue. We derive a solution of a general two-dimensional time dependent radiative transfer equation in a tissue-like medium. The used model is suitable for many situations especially when the external source is time-dependent or continuous. We use a control volume-discrete ordinate method associated with an implicit three-level second-order time differencing scheme. We consider a very thin rectangular biological-tissue-like medium submitted to a visible or a near infrared light sources. The RTE is solved for a set of different wavelength source. All sources are assumed to be monochromatic and collimated. The energetic fluence rate is computed at a set of detector points on the boundaries. According to the source type, we investigate either the steady-state or transient response of the medium. The used model is validated in the case of a heterogeneous tissue-like medium using referencing experimental results from the literature. Also, the developed model is used to study changes on transmitted light in a rat-liver tissue-like medium. Optical properties depend on the source wavelength and they are taken from the literature. In particular, light-transmission in the medium is studied for continuous wave and for short pulse.

scholarly journals Prospect of CW Raman Laser in Silicon- on- Insulator Nano-Waveguides

2020 ◽  
Vol 18 (45) ◽  
pp. 9-20
Author(s):  
Zainab Salam Khaleefia ◽  
Sh. S. Mahdi ◽  
S. Kh. Yaseen
Keyword(s):  
Communication Systems ◽  
Continuous Wave ◽  
Raman Laser ◽  
Silicon On Insulator ◽  
Photon Absorption ◽  
Lasing Threshold ◽  
Free Carrier Absorption ◽  
Carrier Absorption ◽  
Raman Lasing ◽  
On Chip

Numerical analysis predicts that continuous-wave (CW) Raman lasing is possible in Silicon-On-insulator (SOI) nano-waveguides, despite of presence of free carrier absorption. The scope of this paper lies on lasers for communication systems around 1550 nm wavelength. Two types of waveguide structures Strip and Rib waveguides have been incorporated. The waveguide structures have designed to be 220 nm in height. Three different widths of (350, 450, 1000) nm were studied. The dependence of lasing of the SOI Raman laser on effective carrier lifetime was discussed, produced by tow photon absorption. At telecommunication wavelength of 1550 nm, Raman lasing threshold was calculated to be 1.7 mW in Rib SOI waveguide with dimensions width (W= 450 nm) and Length (L= 25 mm). The obtained Raman lasing is the lowest reported value at relatively high reflectivities. Raman laser in SOI nano-waveguides presents the important step towards integrated on-chip optoelectronic devices.

The Role of Free Carrier Absorption in LADA

2014 ◽  
Author(s):  
Kent Erington ◽  
Dan Bodoh ◽  
Kris Dickson ◽  
George Lange
Keyword(s):  
Integrated Circuit ◽  
Continuous Wave ◽  
Free Carrier ◽  
Photon Absorption ◽  
Free Carrier Absorption ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Electron Hole Pair ◽  
Carrier Absorption

Abstract Laser-assisted device alteration (LADA) is an established technique used to identify critical speed paths in integrated circuit. In this paper, the characterization of continuous wave 1340nm laser induced currents and the LADA failure rate show that a two photon absorption explanation for the LADA effect is not plausible. The following sections confirm the results of a 28nm-node nMOS transistor using a 2.45NA solid immersion lens. The effects of global heating to that of local laser heating are then compared. The paper shows that the LADA response time to approximately 1300nm irradiation is << 100ns. It explains LADA at approximately 1300nm, free carrier absorption in the silicon and in the local silicide layers, and presents selected 1320nm LADA images on 28nm-node devices. Finally, it shows 1064nm LADA images on the same structure that indicate that 1064nm interaction with transistors is related to free carrier absorption, rather than electron-hole pair creation.

scholarly journals Laser-induced thermal grating spectroscopy based on femtosecond laser multi-photon absorption

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Maria Ruchkina ◽  
Dina Hot ◽  
Pengji Ding ◽  
Ali Hosseinnia ◽  
Per-Erik Bengtsson ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Laser Pulses ◽  
Photon Absorption ◽  
Gas Flows ◽  
Single Shot ◽  
Photon Excitation ◽  
Fs Laser ◽  
Thermal Grating ◽  
Grating Spectroscopy ◽  
First Time

AbstractLaser-induced grating spectroscopy (LIGS) is for the first time explored in a configuration based on the crossing of two focused femtosecond (fs) laser pulses (800-nm wavelength) and a focused continuous-wave (cw) laser beam (532-nm wavelength). A thermal grating was formed by multi-photon absorption of the fs-laser pulses by $$\hbox {N}_{{2}}$$ N 2 with a pulse energy around 700 $$\upmu $$ μ J ($$\sim $$ ∼ 45 TW/$$\hbox {cm}^{2}$$ cm 2 ). The feasibility of this LIGS configuration was investigated for thermometry in heated nitrogen gas flows. The temperature was varied from room temperature up to 750 K, producing strong single-shot LIGS signals. A model based on the solution of the linearized hydrodynamic equations was used to extract temperature information from single-shot experimental data, and the results show excellent agreement with the thermocouple measurements. Furthermore, the fluorescence produced by the fs-laser pulses was investigated. This study indicates an 8-photon absorption pathway for $$\hbox {N}_{{2}}$$ N 2 in order to reach the $$\hbox {B}^{3}\Pi _{g}$$ B 3 Π g state from the ground state, and 8 + 5 photon excitation to reach the $$\hbox {B}^{2}\Sigma _{u}^{+}$$ B 2 Σ u + state of the $$\hbox {N}_{2}^{+}$$ N 2 + ion. At pulse energies higher than 1 mJ, the LIGS signal was disturbed due to the generation of plasma. Additionally, measurements in argon gas and air were performed, where the LIGS signal for argon shows lower intensity compared to air and $$\hbox {N}_{{2}}$$ N 2 .

scholarly journals Spatial characterization of propagation channels for terahertz band

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Bilal Aghoutane ◽  
Mohammed El Ghzaoui ◽  
Hanan El Faylali
Keyword(s):  
Communication Systems ◽  
Indoor Environment ◽  
Channel Model ◽  
Path Loss ◽  
Propagation Loss ◽  
Terahertz Band ◽  
Indoor Scenarios ◽  
Transmission Windows ◽  
Sv Channel

AbstractThe aim of this work consists in characterizing the Terahertz (THz) propagation channel in an indoor environment, in order to propose a channel model for THz bands. We first described a propagation loss model by taking into account the attenuation of the channel as a function of distance and frequency. The impulse response of the channel is then described by a set of rays, characterized by their amplitude, their delay and their phase. Apart from the frequency selective nature, path loss in THz band is also an others issue associated with THz communication systems. This work based on the conventional Saleh-Valenzuela (SV) model which is intended for indoor scenarios. In this paper, we have introduced random variables as Line of sight (LOS) component, and then merging it with the SV channel model to adopt it to the THz context. From simulation, we noted an important effect when the distance between the transmitter and the receiver change. This effect produces variations in frequency loss. The simulations carried out from this model show that to enhance the performance of THz system it is recommended to transmit information over transmission windows instead over the whole band.

scholarly journals Enhancement of Photoacoustic Signal Strength with Continuous Wave Optical Pre-Illumination: A Non-Invasive Technique

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1190
Author(s):  
Anjali Thomas ◽  
Souradip Paul ◽  
Joy Mitra ◽  
Mayanglambam Suheshkumar Singh
Keyword(s):  
Methylene Blue ◽  
Continuous Wave ◽  
Optical Power ◽  
Signal Strength ◽  
Optical Beam ◽  
Clinical Translation ◽  
Optical Absorption Coefficient ◽  
Invasive Technique ◽  
Light Sources ◽  
Chicken Tissue

Use of portable and affordable pulse light sources (light emitting diodes (LED) and laser diodes) for tissue illumination offers an opportunity to accelerate the clinical translation of photoacoustic imaging (PAI) technology. However, imaging depth in this case is limited because of low output (optical) power of these light sources. In this work, we developed a noninvasive technique for enhancing strength (amplitude) of photoacoustic (PA) signal. This is a photothermal-based technique in which a continuous wave (CW) optical beam, in addition to short-pulse ~ nsec laser beam, is employed to irradiate and, thus, raise the temperature of sample material selectively over a pre-specified region of interest (we call the process as pre-illumination). The increase in temperature, in turn enhances the PA-signal strength. Experiments were conducted in methylene blue, which is one of the commonly used contrast agents in laboratory research studies, to validate change in temperature and subsequent enhancement of PA-signal strength for the following cases: (1) concentration or optical absorption coefficient of sample, (2) optical power of CW-optical beam, and (3) time duration of pre-illumination. A theoretical hypothesis, being validated by numerical simulation, is presented. To validate the proposed technique for clinical and/or pre-clinical applications (diagnosis and treatments of cancer, pressure ulcers, and minimally invasive procedures including vascular access and fetal surgery), experiments were conducted in tissue-mimicking Agar phantom and ex-vivo animal tissue (chicken breast). Results demonstrate that pre-illumination significantly enhances PA-signal strength (up to ~70% (methylene blue), ~48% (Agar phantom), and ~40% (chicken tissue)). The proposed technique addresses one of the primary challenges in the clinical translation of LED-based PAI systems (more specifically, to obtain a detectable PA-signal from deep-seated tissue targets).

Structural characterization of two K2SnX(PO4)3 (X=Fe,Yb) with langbeinite structure

2006 ◽  
Vol 21 (3) ◽  
pp. 214-219 ◽  
Author(s):  
Abderrahim Aatiq ◽  
Btissame Haggouch ◽  
Rachid Bakri ◽  
Youssef Lakhdar ◽  
Ismael Saadoune
Keyword(s):  
Solid State ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Cell Parameter ◽  
Rietveld Analysis ◽  
Conventional Solid State Reaction ◽  
X Ray ◽  
Octahedral Sites ◽  
Parameter Values

Structures of two K2SnX(PO4)3(X=Fe,Yb) phosphates, obtained by conventional solid state reaction techniques at 950 °C, were determined at room temperature by X-ray powder diffraction using Rietveld analysis. The two materials exhibit the langbeinite-type structure (P213 space group, Z=4). Cubic unit cell parameter values are: a=9.9217(4) Å and a=10.1583(4) Å for K2SnFe(PO4)3 and K2SnYb(PO4)3, respectively. Structural refinements show that the two crystallographically independent octahedral sites (of symmetry 3) have a mixed Sn∕X (X=Fe,Yb) population although ordering is stronger in the Yb phase than in the Fe phase.

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