Due to the thermal deposition, the switching ratio of the amplitude OASLM will be reduced, so it is difficult to play a better effect in the high average power laser system. In this paper, through the analysis of laser-induced temperature rise model and liquid crystal layer voltage model and experiments, we show that with the same aperture and same switching ratio, the tolerable optical power density will decrease with the larger irradiation spot area. When the spot diameter decreases from 8 mm to 3 mm without heat dissipation treatment, the temperature of the OASLM emitting surface decreases from 39.6 °C to 33 °C, and the laser tolerated power density improves from 32.8 W/ cm2 to 120 W/ cm2, but the total tolerated power decreases from 16.5 W to 8.5 W. Therefore, in order to improve the total power tolerance of the optical addressable spatial light modulator, it is still an important technical way to improve the clear aperture of the optical addressable spatial light modulator.
We propose a terahertz (THz) vortex emitter that utilizes a high-resistance silicon resonator to generate vortex beams with various topological charges. Addressing the challenge of double circular polarization superposition resulting from the high refractive index contrast, we regulate the transverse spin state through a newly designed second-order grating partially etched on the waveguide’s top side. The reflected wave can be received directly by a linearly polarized antenna, simplifying the process. Benefiting from the tuning feature, a joint detection method involving positive and negative topological charges identifies and detects rotational Doppler effects amid robust micro-Doppler interference signals. This emitter can be used for the rotational velocity measurement of an on-axis spinning object, achieving an impressive maximum speed error rate of ∼2 % . This approach holds promise for the future development of THz vortex beam applications in radar target detection and countermeasure systems, given its low cost and potential for mass production.
The influence of the inner disk radius r, the filling ratio α, numbers of sectors N, and the gap g on transmission response for corrugated metallic disk (CMD) with single C-shaped resonator(CSR) has been fully studied. The results indicate that varying parameters r can efficiently excite the higher order spoof localized surface plasmon modes in corrugated metallic disk. The relationship between the bright dipole and dark multipolar resonances presents the possibility of high Q dark resonances excitation. All results may be of great interest for diverse applications.
The influence of the waveguide spacing on transmission response for parallel-plate waveguide with single deep groove has been experimentally studied. The results indicate that the decrease of spacing can efficiently excite the higher order cavity modes in very deep groove. The relationship between the spacing and the channel number presents the possibility of a notch filter to mechanically select the channel number. Experimental data and simulations results verify this channel number tunibility, which may be of great interest for communication applications.
The Faraday magneto-optical effect of optical fiber has many applications in monitoring magnetic field and electric current. When a linearly polarized light propagates in the direction of a magnetic field, the plane of polarization will rotate linearly proportional to the strength of the applied magnetic field, which following the relationship of θF =VBl. θF is the Faraday rotation angle, which is proportional to the magnetic flux density B and the Verdet constant V .
However, when the optical fiber contains the effect of linear birefringence, the detection of Faraday rotation angle will depend on the line birefringence. In order to determine the Verdet constant of an optical fiber under a linear birefringence, the fiber birefringence needs to be accurately measured. In this work, a model is applied to analyze the polarization properties of an optical fiber by using the Jones matrix method. A measurement system based on the lock-in amplifier technology is designed to test the Verdet constant and the birefringence of optical fiber. The magnetic field is produced by a solenoid with a DC current. A tunable laser is intensity modulated with a motorized rotating chopper. The actuator supplies a signal as the phase-locked synchronization reference to the signal of the lock-in amplifier. The measurement accuracy is analyzed and the sensitivity of the system is optimized. In this measurement system, the Verdet constant of the SMF-28 fiber was measured to be 0.56±0.02 rad/T·m at 1550nm. This setup is well suitable for measuring the high signal-to-noise ratio (SNR) sensitivity for lock-in amplifier at a low magnetic field strength.
This paper puts forward a newer sensor which is symmetrical two rectangular resonant cavities based on parallel-plate
waveguide, using the lowest-order transverse-electric mode in terahertz region . From the simulation result we found when
we place the material in one of the resonant cavity, the original symmetric state has changed, not only a new resonance peak
appear ,but it also every resonant peak has obvious relative frequency shift with different material. So the structure can be used
as the sensor, which can detect the material.
A metal hole arrays terahertz filter based on surface plasmon polaritons and fabricated by aluminum slab of different holes scales have been experimentally investigated by using THz time-domain spectroscopy system from 0.1 to 2.7 THz. The experiment results indicated there is a transmission peak at 0.26 THz, approximately. The results in simulation by finite element method agree well with the experimental one for the big scale sample. The mismatch of experimental and simulated results for small scale sample can be attributed to boundary condition and insufficient periodical extension. Further, the theoretical analyses about extraordinary optical transmission and filter phenomena are also discussed.
Theoretical and experimental works were carried out on a double channel mechanically tunable terahertz filter integrated with parallel plate waveguide cavities. The filter includes two rectangular grooves on upper and bottom plates of waveguide, respectively. The filter frequencies can be quasilinearly tuned by altering the overlap length between two rectangle grooves on metal plates. From the experiment, we found low (high) resonant frequency can be adjusted from 0.417(0.346) THz to 0.399(0.374) THz when the overlap length is altered from 0 to 500 μm, respectively. The Q values can reach 46 with the resonant frequency (0.41THz), overlap length (220 μm) and waveguide spacing (650 μm). Theoretical results show good agreement with experiment.
Large positive and negative Goos-Hänchen(GH) shifts on an symmetrical metal-cladding waveguide (SMCW) were
investigated both theoretically and experimentally. The SMCW is simply a glass slab with several hundred micrometers
sandwiched between two gold films. A recently developed free-space coupling technique was used to transfer the light
energy into the ultrahigh order modes of the SMCW. It is shown that during the resonant excitation, and the intrinsic
damping coincides with the radiative damping of the modes, the lateral shifts of reflected beam are enhanced to as large
as hundreds of micrometers. It is also known that sign of the GH shift is totally dependent on the difference between the
radiative damping and the intrinsic damping. GH shifts with sub-millimeter scale were experimentally observed. The
experimental results show good agreement with theoretical prediction.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.