排序方式: 共有35条查询结果,搜索用时 625 毫秒
1.
M. Pollnau E. Heumann G. Huber 《Applied Physics A: Materials Science & Processing》1992,54(5):404-410
A pump- and probe-beam technique is used for measuring time-resolved excited-state absorption (ESA) and stimulated-emission (SE) spectra of Er3+ doped YAlO3. The Er3+
4
I
15/2 4
F
7/2 transition of the sample is excited at 488 nm by an excimer laser pumped dye laser. The ESA and SE of broadband xenon flashlamp light is monitored between 300 and 860 nm by an optical multichannel analyzer (OMA). The analysis of the experimental results provides information on the effective cross sections ESA and SE originating from several levels and on the populations of these levels. To our knowledge this represents the first detailed investigation of time-resolved ESA and SE over a broad spectral range in rare-earth doped materials. 相似文献
2.
Ismail N Choo-Smith LP Wörhoff K Driessen A Baclig AC Caspers PJ Puppels GJ de Ridder RM Pollnau M 《Optics letters》2011,36(23):4629-4631
An integrated arrayed-waveguide grating fabricated in silicon-oxynitride technology is applied to Raman spectroscopy. After its validation by reproducing the well-known spectrum of cyclohexane, polarized Raman spectra are measured of extracted human teeth containing localized initial carious lesions. Excellent agreement is obtained between the spectra of healthy and carious tooth enamel measured with our integrated device and spectra recorded using a conventional Raman spectrometer. Our results represent a step toward the realization of compact, hand-held, integrated spectrometers, e.g. for the detection of dental caries at an early stage. 相似文献
3.
M. Pollnau W. Lüthy H. P. Weber K. Krämer H. U. Güdel R. A. McFarlane 《Applied physics. B, Lasers and optics》1996,62(4):339-344
The influence of Excited-State Absorption (ESA) on the green laser transition and the overlap of Ground-State Absorption (GSA) and ESA for 970 nm upconversion pumping in erbium is investigated in Er3+ : BaY2F8 and Cs3Er2Br9. Results are compared to Er3+ : LiYF4. In Er3+: BaY2F8, a good overlap between GSA and ESA is found at 969 nm in one polarization direction. The emission cross section at 550 nm is a factor of two smaller than in LiYF4. In Cs3Er2Br9, the smaller Stark splitting of the levels shifts the wavelengths of the green emission and ESA from4
I
1 3/2 off resonance. It enhances, however, ground-state reabsorption. The emission cross section at 550 nm is comparable to LiYF4. Upconversion leads to significant green fluorescence from2
H
9/2. A significant population of the4
I
11/2 level and ESA at 970 nm are not present under 800 nm pumping. 相似文献
4.
Edward H. Bernhardi Kees O. van der Werf Anton J. F. Hollink Kerstin Wrhoff Ren M. de Ridder Vinod Subramaniam Markus Pollnau 《Laser \u0026amp; Photonics Reviews》2013,7(4):589-598
An integrated intra‐laser‐cavity microparticle sensor based on a dual‐wavelength distributed‐feedback channel waveguide laser in ytterbium‐doped amorphous aluminum oxide on a silicon substrate is demonstrated. Real‐time detection and accurate size measurement of single micro‐particles with diameters ranging between 1 µm and 20 µm are achieved, which represent the typical sizes of many fungal and bacterial pathogens as well as a large variety of human cells. A limit of detection of ∼500 nm is deduced. The sensing principle relies on measuring changes in the frequency difference between the two longitudinal laser modes as the evanescent field of the dual‐wavelength laser interacts with micro‐sized particles on the surface of the waveguide. Improvement in sensitivity far down to the nanometer range can be expected upon stabilizing the pump power, minimizing back reflections, and optimizing the grating geometry to increase the evanescent fraction of the guided modes. 相似文献
5.
Dongre C Dekker R Hoekstra HJ Pollnau M Martinez-Vazquez R Osellame R Cerullo G Ramponi R van Weeghel R Besselink GA van den Vlekkert HH 《Optics letters》2008,33(21):2503-2505
Using femtosecond laser writing, optical waveguides were monolithically integrated into a commercial microfluidic lab-on-a-chip device, with the waveguides intersecting a microfluidic channel. Continuous-wave laser excitation through these optical waveguides confines the excitation window to a width of 12 microm, enabling high-resolution monitoring of the passage of different types of fluorescent analytes when migrating and being separated in the microfluidic channel by microchip capillary electrophoresis. Furthermore, we demonstrate on-chip-integrated waveguide excitation and detection of a biologically relevant species, fluorescently labeled DNA molecules, during microchip capillary electrophoresis. Well-controlled plug formation as required for on-chip integrated capillary electrophoresis separation of DNA molecules, and the combination of waveguide excitation and a low limit of detection, will enable monitoring of extremely small quantities with high spatial resolution. 相似文献
6.
S. García-Revilla R. Valiente Y.E. Romanyuk M. Pollnau 《Journal of luminescence》2008,128(5-6):934-936
Crystalline Er3+ and Yb3+ singly and doubly doped KY(WO4)2 thin films were grown by low-temperature liquid-phase epitaxy. Absorption, luminescence, excitation and temporal evolution measurements were carried out for both Er3+ and Yb3+ transitions from 10 K to room temperature. Green Er3+ upconversion luminescence was observed after Yb3+ and Er3+ excitation. The mechanisms responsible for the upconversion phenomena detected in each case were identified. 相似文献
7.
R. Osellame H.J.W.M. Hoekstra G. Cerullo M. Pollnau 《Laser \u0026amp; Photonics Reviews》2011,5(3):442-463
This paper provides an overview of the rather new field concerning the applications of femtosecond laser microstructuring of glass to optofluidics. Femtosecond lasers have recently emerged as a powerful microfabrication tool due to their unique characteristics. On the one hand, they enable to induce a permanent refractive index increase, in a micrometer‐sized volume of the material, allowing single‐step, three‐dimensional fabrication of optical waveguides. On the other hand, femtosecond‐laser irradiation of fused silica followed by chemical etching enables the manufacturing of directly buried microfluidic channels. This opens the intriguing possibility of using a single laser system for the fabrication and three‐dimensional integration of optofluidic devices. This paper will review the state of the art of femtosecond laser fabrication of optical waveguides and microfluidic channels, as well as their integration for high sensitivity detection of biomolecules and for cell manipulation. 相似文献
8.
We report on an upconversion cascade laser in an erbium-doped ZBLAN fiber emitting simultaneously on the three transitions (4)S(3/2) ? (4)I(9/2) at 1.7 microm , (4)I(11/2) ? (4)I(13/2) at 2.7 microm , and (4)I(13/2) ? (4)I(15/2) at 1.6 microm . At moderate pump powers, the laser transition at 1.6 microm supports 2.7-microm lasing and permits a slope efficiency at 2.7 microm of 15% versus launched pump power. Above the threshold of upconversion lasing at 1.7 microm , the slope efficiency at 2.7 microm increases to 25.4%. Taking pump excited-state absorption into account, this value represents more than 90% of the theoretical slope efficiency. A transversely single-mode output power of 99mW is achieved at 2.7 microm. 相似文献
9.
Martinez Vazquez R Osellame R Cretich M Chiari M Dongre C Hoekstra HJ Pollnau M van den Vlekkert H Ramponi R Cerullo G 《Analytical and bioanalytical chemistry》2009,393(4):1209-1216
We use direct femtosecond laser writing to integrate optical waveguides into a commercial fused silica capillary electrophoresis
chip. High-quality waveguides crossing the microfluidic channels are fabricated and used to optically address, with high spatial
selectivity, their content. Fluorescence from the optically excited volume is efficiently collected at a 90° angle by a high
numerical aperture fiber, resulting in a highly compact and portable device. To test the platform we performed electrophoresis
and detection of a 23-mer oligonucleotide plug. Our approach is quite powerful because it allows the integration of photonic
functionalities, by simple post-processing, into commercial LOCs fabricated with standard techniques.
Figure Femtosecond laser written waveguides can selectively excite fluorescence in a microfluidic channel of a commercial lab-on-a-chip.
A compact scheme for on-chip detection by laser induced fluorescence is applied to capillary electrophoresis of a 23-mer Cy3-labeled
oligonucleotide 相似文献
10.
EH Bernhardi MR Khan CG Roeloffzen HA van Wolferen K Wörhoff RM de Ridder M Pollnau 《Optics letters》2012,37(2):181-183
We report the fabrication and characterization of a dual-wavelength distributed-feedback channel waveguide laser in ytterbium-doped aluminum oxide. Operation of the device is based on the optical resonances that are induced by two local phase shifts in the distributed-feedback structure. A stable microwave signal at ~15 GHz with a -3?dB width of 9 kHz was subsequently created via the heterodyne photodetection of the two laser wavelengths. The long-term frequency stability of the microwave signal produced by the free-running laser is better than ±2.5 MHz, while the power of the microwave signal is stable within ±0.35 dB. 相似文献