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Cavity Length (cavity + length)
Selected AbstractsExperimental investigation into femtosecond fiber ring laser with passive mode lockingMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2009Xiaoping Xie Abstract A passively mode-locked Er3+ -doped fiber ring laser is experimentally investigated, with the emphasis on its practical design by considering the effects of ring cavity length, pumping light power, and optical amplification on the femtosecond optical pulses obtained. It is shown that the designed fiber ring laser can operate at the center wavelength of 1550 nm to produce a train of periodic optical pulses with full width at half maximum (FWHM) of 270 fs, repetition frequency of 20 MHz, and average output optical power of 146 ,W. The resulting femtosecond optical pulses are then amplified by using three kinds of Er3+ -doped optical fibers with different lengths and Er3+ -doped concentrations, respectively, while employing the same pumping laser. In the experiments, both the FWHM of amplified optical pulses and the amplifier gain are measured under different conditions. The optimization of optical pulse width is also carried out in terms of pumping light power. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 63,67, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23985 [source] Length dependence of polarization in spontaneous edge emissions from InGaN/AlGaN MQWs laser diodesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2007Chuanyu Jia Abstract The polarization of spontaneous edge-emitting electroluminescence from near-UV LDs with different cavity lengths (from 400 ,m to 1000 ,m) was studied. It was found that TE mode dominates in InGaN/AlGaN MQWs LDs, which is consistent with the theoretical calculation results of similar MQWs. An obvious polarization decrease from P = 0.57 to 0.42 as the LD cavity length changed from 400 ,m to 1000 ,m was also observed, corresponding to a ratio r changing from 3.67 to 2.43, which indicated that, the TE mode attenuated more grievously than the TM mode with increasing cavity length. This is due to the inherent property of polarization selective emission from the alloys. The optical loss coefficient of TE mode was determined to be 35 cm,1, while, 10 cm,1 for TM mode, which is in good agreement with the results obtained from other methods. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Reflectance and photoluminescence studies of InGaN/GaN multiple-quantum-well structures embedded in an asymmetric microcavityPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2006D. Y. Lin Abstract Using reflectance (R) and photoluminescence (PL) measurements InGaN/GaN multiple-quantum-well (MQW) structures embedded in an asymmetric microcavity with different thickness of stacking pairs have been studied. The asymmetric microcavity structures are composed of a cavity sandwitched between the air/semiconductor interface and a mirror using distributed Bragg reflector (DBR). For the DBR with thinner AlN layers the high-reflectivity stop band locates at higher photon energy. The luminescence efficiency and the spectrum of InGaN/GaN multiple-quantum-well structures will be modified by the microcavity. A comparison of PL with R spectra shows that the emission efficiency can be enhanced by matching up the luminescence spectrum coming from the MQW and the high-reflectivity stop band. From the blue shift of the cavity modes as a function of incident angles the refractive index and cavity length can be determined. By measuring the PL spectra as a function of emission angle, it is found that the PL spectra were predominatly determined by microcavity resonances. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Left ventricular end-diastolic geometrical adjustments during exercise in endurance athletesCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 2 2008Egil Henriksen Summary The increase in left ventricular (LV) end-diastolic volume has recently been shown to explain more than 70% of the increase in stroke volume during upright exercise in endurance athletes. As the end-diastolic volume enhancement not could be explained by an increase in axial cavity length an augmentation in LV short-axis diameters is to be expected. To investigate LV end-diastolic geometrical alterations during exercise, 15 endurance athletes were examined using contrast exercise echocardiography. LV end-diastolic short-axis diameters were made from apical views at several LV cavity levels. From upright rest to upright exercise the LV end-diastolic internal cavity measurements increased significantly. During exercise, the LV cavity became geometrically more spherical with the largest increase in the LV end-diastolic short-axis cavity diameters in the mid and apical parts of the left ventricle. The LV internal long axis showed significant increase from rest to exercise but the absolute increase was small. [source] Analyzing longitudinal-mode of single-frequency ring fiber laserMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2007T. S. Wang Abstract To realize single-frequency of the fiber laser, a ring configuration is devised. The single-frequency operation is realized at 1549.63 nm by using a fiber Bragg grating (FBG) as wavelength-selective element and a unpumped 1.5 m-long erbium-doped fiber, which can produce standing-wave saturation effects in the cavity. A measurement method based on fiber-coupling scanning Fabry,Perot (F-P) interferometer at 1.55 ,m is designed. The laser longitudinal-mode spacing is 11.1 MHz. The single-frequency is observed by the interferometer with free spectrum range (FSR) of 7.5 GHz. The longitudinal-mode fabric is analyzed by the interferometer with FSR of 1.5 GHz. As the cavity length increases, the longitudinal-mode spacing changes to 3.7 MHz. The structures of longitudinal-modes under different cavity lengths are compared. The longitudinal-mode linewidth of 20 MHz is measured. Experimental results show that single-frequency of the fiber laser can be approved accurately, and the effectiveness of the method, which can analyze longitudinal-mode of the fiber laser with scanning Fabry,Perot (F-P) interferometer, is improved. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1494,1497, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22467 [source] Length dependence of polarization in spontaneous edge emissions from InGaN/AlGaN MQWs laser diodesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2007Chuanyu Jia Abstract The polarization of spontaneous edge-emitting electroluminescence from near-UV LDs with different cavity lengths (from 400 ,m to 1000 ,m) was studied. It was found that TE mode dominates in InGaN/AlGaN MQWs LDs, which is consistent with the theoretical calculation results of similar MQWs. An obvious polarization decrease from P = 0.57 to 0.42 as the LD cavity length changed from 400 ,m to 1000 ,m was also observed, corresponding to a ratio r changing from 3.67 to 2.43, which indicated that, the TE mode attenuated more grievously than the TM mode with increasing cavity length. This is due to the inherent property of polarization selective emission from the alloys. The optical loss coefficient of TE mode was determined to be 35 cm,1, while, 10 cm,1 for TM mode, which is in good agreement with the results obtained from other methods. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Internal parameters and optical properties of green II-VI heterostructure lasers with active region composed of multi-sheet electronically-coupled CdSe quantum dotsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2010Aliaksei G. Vainilovich Abstract Optically pumped green-emitting ZnSe-based laser heterostructures of optimized design have been grown by molecular-beam epitaxy and studied. The structures containing five electronically-coupled stacked CdSe quantum dot (QD) sheets demonstrate the minimum threshold power density of 2.2 kW/cm2 and the maximum external quantum efficiency of , 50%. Internal laser characteristics were determined by measuring the differential laser efficiency and laser threshold of a series of samples with different cavity lengths. The characteristic gain and internal quantum efficiency of the structures have been shown to reach the values as high as ,G0 = 114 cm -1 and ,i = 65.4%, while the transparency threshold and internal losses are evaluated as low as IT = 1.22 kW/cm2 and ,i = 2.55 cm -1, respectively. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||