共查询到20条相似文献,搜索用时 15 毫秒
1.
We report on the fabrication of hollow optical waveguides in fused silica using femtosecond laser micromachining. We show
that in such hollow waveguides, high-intensity femtosecond laser beams can be guided with low optical loss. Our technique,
which was established earlier for fabrication of optofluidic structures in glass, can ensure a high smoothness at the inner
surfaces of the hollow waveguides and provide the unique capability of fabrication of hollow waveguides with complex geometries
and configurations. A transmission of ∼90% at 633 nm wavelength is obtained for a 62-mm-long hollow waveguide with an inner
diameter of ∼250 μm. In addition, nonlinear propagation of femtosecond laser pulses in the hollow waveguide is demonstrated,
showing that the spectral bandwidth of the femtosecond pulses can be broadened from ∼27.2 to ∼55.7 nm. 相似文献
2.
A Bragg waveguide is analyzed from the viewpoint of obtaining slow light. It is shown that, for this system, a complete mathematical
analysis of the pulse propagation with allowance for leakage is possible. Calculations are presented that show that, in a
TiO2/SiO2-based Bragg waveguide, one can obtain a group index of ∼1000 with a spatial decay length of ∼3 mm for a nanosecond-scale
pulse. Distortion of the pulse due to the group index dispersion proves to be acceptable, in this case, for the pulse propagation
length of about 3 mm, which corresponds to the fractional pulse delay ∼10. We also analyze the propagation of the light pulse
in the Bragg waveguide with a quantum well inside and show possibility of obtaining a group index of ∼10000. 相似文献
3.
Taking advantage of the different cut-off thickness of the two fundamental modes in an optical waveguide, a polarizing structure
has been realized. It consists of a narrow stripe (∼100 μm) of reduced diffusion depth in an ion-exchanged waveguide. The
TE0-mode passes the polarizer with negligible losses, whereas the TM0-mode is forced to couple out into the substrate. The extinction ratio is better than −16 dB. 相似文献
4.
We present a diode-end-pumped Nd:YAG planar waveguide laser operating on neodymium’s quasi-four-level transition at a wavelength
of 946 nm. Two modes of operation are described: a high-power multi-mode monolithic cavity generating 105 for 210 W of incident
pump power with a slope efficiency of ∼54%, and secondly, a high-radiance configuration employing an external stable resonator
producing a maximum output power of 29.2 for 86.5 W of incident pump-power, with a slope efficiency of 33%. The output beam
quality values of the external cavity were M2 of 3.2 by 2.4, leading to a maximum radiance of 0.43 GW cm−2 sr−1. 相似文献
5.
We design a multi-layer cladding large-core planar waveguide that supports a single guided mode. The waveguide works on the
principle of higher-order mode discrimination. The cladding of the waveguide is formed by alternate low- and high- index regions,
which helps leaking out of higher-order modes while retaining the fundamental mode over the entire length of the waveguide.
The structure is analyzed by the transfer-matrix method and the leakage losses of the modes have been calculated. We show
that a waveguide formed in silica with numerical aperture 0.24 and core width 10 μm can be designed to exhibit single-mode
operation at 1550-nm wavelength. Such a structure should find applications in high-power planar waveguide lasers and amplifiers. 相似文献
6.
M. Andachi T. Nakayama M. Kawasaki S. Kurokawa H.-P. Loock 《Applied physics. B, Lasers and optics》2007,88(1):131-135
Visible and near-infrared laser light pulses were coupled into two different types of optical fiber cavities. One cavity consisted
of a short strand of fiber waveguide that contained two identical fiber Bragg gratings. Another cavity was made using a loop
of optical fiber. In either cavity ∼40 ps laser pulses, which were generated using a custom-built gain-switched diode laser,
circulated for a large number of round trips. The optical loss of either cavity was determined from the ring-down times. Cavity
ring-down spectroscopy was performed on 200 pL volumes of liquid samples that were injected into the cavities using a 100 μm
gap in the fiber loop. A detection limit of 20 ppm of methylene blue dye in aqueous solution, corresponding to a minimum absorptivity
of εC<6 cm-1, was realized.
PACS 42.62.Fi; 42.81.-i 相似文献
7.
Tunable dual-wavelength fiber laser based on a polarization-maintaining fiber Bragg grating and a Hi-Bi fiber optical loop mirror 总被引:1,自引:0,他引:1
R. I. Álvarez-Tamayo M. Durán-Sánchez O. Pottiez E. A. Kuzin B. Ibarra-Escamilla 《Laser Physics》2011,21(11):1932-1935
We demonstrate experimentally the operation of a linear cavity dual-wavelength fiber laser using a polarization maintaining
fiber Bragg grating (PM-FBG) as an end mirror that defines two closely spaced laser emission lines. The PM-FBG is also used
to tune the laser wavelengths. The total tuning range is ∼8 nm. The laser operates in a stable dual-wavelength mode for an
appropriate adjustment of the cavity losses for the generated wavelengths. The high birefringence (Hi-Bi) fiber optical loop
mirror (FOLM) is used as a tunable spectral filter to adjust the losses. The FOLM adjustment was performed by the temperature
control of the Hi-Bi fiber. 相似文献
8.
We report optical planar waveguide formation and modal characterization in β-BaB2O4 crystals by Cu2+-ion implantation at an energy of 3.0 MeV and doses of ∼ 1014 ions/cm2. The prism-coupling method was used to investigate the dark-mode property at wavelengths of 633 nm and 1539 nm. The refractive-index
profile of the waveguide was reconstructed by an effective refractive index method. The modal analysis indicates that the
fields of TM modes can be well restricted in the guiding region, which means the formation of a non-leaky waveguide in the
crystal. The results show that the β-BaB2O4 waveguides may be used in the application of high efficiency frequency conversion.
PACS 61.80.Jh; 42.70.Mp; 42.65.Wi 相似文献
9.
We report on the generation of continuous wave lasers at a wavelength of ∼1064 nm in a Nd:YAG ceramic waveguide at room temperature.
The waveguide was fabricated by using 6 MeV carbon ion implantation at a fluence of 3×1014 ions/cm2. Laser operation has been realized with a slope efficiency as high as ∼11%. The pump threshold of an 808-nm laser beam for
the waveguide laser oscillation is 19.5 mW. 相似文献
10.
A multimode model is developed to determine optical losses in a waveguide laser cavity of cylindrical symmetry with mirrors
of arbitrary radius of curvature. Within the framework of the model, it is possible to vary the parameters of the resonator:
waveguide length, distance between the waveguide and mirrors, radius of curvature of the mirrors in a wide range taking account
of mutual conversion of up to 10 waveguide modes and 20 modes of free space. The model was applied successfully to determine
the optimal geometry of a semiconfocal cavity.
A. N. Sevchenko Scientific-Research Institute of Physical Problems, 7 Kurchatov Str., Minsk, 220064, Belarus; e-mail: v.saetchnikov@rfe.bsu.unibel.by.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 6, pp. 779–783, November–December, 1999. 相似文献
11.
Cavity ringdown (CRD) spectroscopy, with its high sensitivity, provides a novel way to perform continuous-wave (cw) stimulated
Raman gain (SRG) spectroscopy, rather than by conventional optically detected coherent Raman techniques. Tunable cw laser
light at ∼1544 nm is used to probe ringdown decay from a rapidly-swept, high-finesse optical cavity containing a gas-phase
sample of interest and itself located inside the cavity of a cw single-longitudinal-mode Nd:YAG ring laser operating at ∼1064.4
nm. This approach is used to measure cw SRG spectra of the ν
1 fundamental rovibrational Raman band of methane gas at ∼2916.5 cm−1. The resulting SRG-CRD resonances have ringdown times longer than in the off-resonance case, in contrast to the usual shorter
ringdown times arising from absorption and other loss processes. Previously reported noise-equivalent sensitivities have been
substantially improved, by using a second ringdown cavity to facilitate subtraction of infrared-absorption background signals.
Moreover, by employing a ringdown cavity in the form of a ring, the SRG-pump and CRD-detected Stokes beams can co-propagate
uni-directionally, which significantly reduces Doppler broadening. 相似文献
12.
A. Crunteanu M. Pollnau G. Jänchen C. Hibert P. Hoffmann R.P. Salathé R.W. Eason C. Grivas D.P. Shepherd 《Applied physics. B, Lasers and optics》2002,75(1):15-17
We report, to our knowledge, the first active channel waveguide in Ti:sapphire. We have created ∼1.4-μm high ribs in a ∼10-μm
thick Ti:sapphire planar waveguide by reactive ion etching. Following excitation by an Ar-ion laser, the rib structure showed
channel-waveguide fluorescence emission. The mode profiles and the beam-parameter values (M2) were measured. The coupling efficiency of fluorescence emission into a single-mode fiber was an order of magnitude higher
than for fluorescence from unstructured planar regions of the waveguide. Such devices are of interest as low-threshold tunable
lasers and as broadband light sources in low-coherence interferometry.
Received: 22 December 2002 / Revised version: 30 March 2002 / Published online: 8 August 2002 相似文献
13.
T. Wu W. Chen E. Fertein F. Cazier D. Dewaele X. Gao 《Applied physics. B, Lasers and optics》2012,106(2):501-509
We report on the development of an optical instrument based on incoherent broadband cavity-enhanced absorption spectroscopy
(IBBCEAS) for simultaneous open-path measurements of nitrous acid (HONO) and nitrogen dioxide (NO2) in ambient air using a UV light emitting diode operating at ∼366 nm. Detection limits of ∼430 pptv for HONO and ∼1 ppbv
for NO2 were achieved with an optimum acquisition time of 90 s, determined by an Allan variance analysis. Based on a 1.85 m long
high optical finesse open-path cavity, the effective optical path length of 2.8 km was realized in aerosol-free samples or
in an urban environment at modest aerosol levels. Such a kilometer long optical absorption is comparable to that achieved
in the well established differential optical absorption spectroscopy (DOAS) technology while keeping the instrument very compact.
Open-path detection configuration allows one to avoid absorption cell wall losses and sampling induced artifacts. The demonstrated
sensitivity and specificity shows high potential of this cost-effective and compact infrastructure for future field applications
with high spatial resolution. 相似文献
14.
M.A. Bader A. Selle O. Stenzel R. Delmdahl G. Spiecker C. Fischer 《Applied physics. B, Lasers and optics》2007,89(2-3):151-154
A high spectral resolution analysis of narrowband reflection filters based on resonant grating waveguide structures is presented.
A tunable high-performance dye laser with ∼ 0.15 cm-1 line width and a beam analyzing system consisting of three simultaneously controlled CCD cameras were used to investigate
grating waveguide resonances at wavelengths in the 694 nm and 633 nm ranges. A reflectivity of ∼ 91% and a line width of ∼ 0.55 nm
were measured and theoretically modeled for a resonant reflection filter specifically designed for the ruby laser wavelength
694.2 nm. For a second grating waveguide structure, designed for the helium-neon laser emission wavelength 632.8 nm, we observed
a thermal shift of its spectral resonance position of several nanometers, when increasing the sample temperature by some degrees.
An inverse thermal shift was observed when the structure was subsequently cooled down to room temperature. Our results suggest
implementation of grating waveguide devices combining a narrow line width with a tunability of the resonant response into
innovative concepts for reflection filter and sensor applications.
PACS 42.62.-b; 42.79.Dj; 42.79.Gn 相似文献
15.
Q. X. Mu Y. H. Ma L. Zhou 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(3):375-379
We present a method of generating two-mode single atom
laser based on the nonresonant interaction of a three-level
Λ type atom in a two-mode cavity with three strong classical
driving fields. An analytical solution for this effective dynamics
under the presence of the cavity losses is obtained, which allow us
to analyze the entanglement properties and the photon statistics of
the two cavity modes exactly. It is also shown that the possible
generation of the two-mode entangled coherent states in the
transient regime after the atomic measurement. 相似文献
16.
V. D. Zvorykin A. O. Levchenko A. G. Molchanov I. V. Smetanin N. N. Ustinovskii 《Bulletin of the Lebedev Physics Institute》2010,37(2):60-64
The grazing mode of microwave propagation in a hollow plasma waveguide formed by ionization of atmospheric air with a small
easily ionized additive by strong UV pulses of the Garpun KrF laser (λ = 248 nm, the pulse duration and energy are ∼70 ns and ∼50 J) was experimentally demonstrated for the first time. The annular
laser beam produced a hollow tube ∼10 cm in diameter with an electron density of ∼1012 cm−3 in a plasma wall ∼1 cm thick, over whichmicrowave radiation with λ
mw
∼ 8 mm was transmitted to a distance of 60 m. Themicrowave signal transmitted by the waveguide was amplified by a factor
of 6 in comparison with propagation in free space. 相似文献
17.
R. An Y. Li D. Liu Y. Dou F. Qi H. Yang Q. Gong 《Applied Physics A: Materials Science & Processing》2007,86(3):343-346
We investigated the femtosecond laser writing of optical waveguides inside Foturan glass at various pulse energies and focusing
depths. An optimal waveguide fabricated solely by femtosecond laser irradiation showed a refractive index modulation of ∼1.7×10-3 and a minimum transmission loss of ∼0.80 dB/cm. This type of waveguide had lower transmission loss than those fabricated
by a hybrid process of femtosecond laser exposure and following thermal treatment. An optical splitter was also fabricated
at high pulse energy.
PACS 42.65.Re; 42.82.Et; 42.70.Gi 相似文献
18.
D. Liu Y. Li R. An Y. Dou H. Yang Q. Gong 《Applied Physics A: Materials Science & Processing》2006,84(3):257-260
We studied the influence of focusing depth on the index change threshold and damage threshold of silica glass irradiated by a focused 120 fs laser beam. Both thresholds increased with the focusing depth. The aspect ratio of the waveguide cross section can be selected by changing the focusing depth. A 5 mm long waveguide was written at the depth of 2100 μm, which was single mode at 632.8 nm and exhibited propagation loss of 0.56 dB/cm. The refractive index change was calculated to be ∼2.47×10-3. The influence of the focusing depth should be considered in multi-layer devices as shown in the fabrication of a 3×3 waveguide array. PACS 42.62.-b; 42.82.Et; 81.05.Kf 相似文献
19.
Molecular vibrations of C2H2 and C2D2 adsorbed on Pt(111) at 140 K and ∼300K have been measured by high resolution electron energy loss spectroscopy. The comparison
of C2H2 and C2D2 spectra allows an unambiguous assignment of the observed losses to the excitation of C−H bending, C−H stretching, and C−C
stretching modes of nondissociatively adsorbed acetylene. From the relative intensities of losses the hybridisation state
is determined to be nearsp
2. The C−C stretching frequency indicates a C−C bond order of ∼1.8. 相似文献
20.
Ning Ou-Yang Jun-Li Wang Ping Zhang Hai Pang 《International Journal of Theoretical Physics》2009,48(3):743-754
Based on the result of cavity quantum electrodynamics, we suggest a method, in which the Fabry-Perot cavity or the confocal
cavity is replaced by a waveguide with the size comparable to the wavelength of the photon, to reduce decoherence caused by
spontaneous emission in quantum information processing, especially in the realization of quantum computation. Since a waveguide
has a lowest cutoff frequency while a Fabry-Perot cavity or a confocal cavity has none, the spontaneous emission of excited
atoms will be forbidden in an ideal waveguide with an appropriate size. To avoid the influence of the non-ideal conducting
walls on the atom in a realistic waveguide, which will lead to decoherence, we suggest that the waveguide should be coated
by a thin film of transparent insulating medium. In our method, the quantum information is represented by a multi-level atom
or molecule; any two of its levels can be used to represent a qubit in principle. Our method greatly extends the choice of
the material to be used in the realization of quantum computation, and it can be used in most schemes to reduce the decoherence
caused by spontaneous emission. 相似文献