Polarization Rotation Effect Research Articles

Stable and Widely Tunable Single-Longitudinal-Mode Dual-Wavelength Erbium-Doped Fiber Laser for Optical Beat Frequency Generation

A stably and widely tunable single-longitudinal-mode dual-wavelength erbium-doped fiber (EDF) laser is investigated for the generation of a tunable optical beat frequency. The lasing wavelength spacing is widely controlled in a range from 3.46 to 13.2 nm, which means that the tunable optical beat frequency in a range from 0.43 to 1.66 THz can be achieved. Nonlinear polarization rotation effect is implemented to stabilize and equalize outputs of the tunable dual-wavelength EDF laser. Since the dual-wavelength fiber laser has a single-longitudinal mode, the proposed dual-wavelength fiber laser is stable.

Giant nonlinear optical activity in a plasmonic metamaterial

In 1950, a quarter of a century after his first-ever nonlinear optical experiment when intensity-dependent absorption was observed in uranium-doped glass, Sergey Vavilov predicted that birefringence, dichroism and polarization rotatory power should be dependent on light intensity. It required the invention of the laser to observe the barely detectable effect of light intensity on the polarization rotatory power of the optically active lithium iodate crystal, the phenomenon now known as the nonlinear optical activity, a high-intensity counterpart of the fundamental optical effect of polarization rotation in chiral media. Here we report that a plasmonic metamaterial exhibits nonlinear optical activity 30 million times stronger than lithium iodate crystals, thus transforming this fundamental phenomenon of polarization nonlinear optics from an esoteric phenomenon into a major effect of nonlinear plasmonics with potential for practical applications.

Picosecond pulse contrast enhancement by use of polarization rotation in crystals with the second-order nonlinearity

We report on the implementation of intensity-dependent filter for picosecond pulse temporal cleaning based on an effect of pulse polarization rotation during the unbalanced phase matched second harmonic generation. The pulse contrast enhancement by more than two orders of magnitude and filter transmission of ∼25% has been demonstrated at pulse intensities of <1 GW/cm2. A simple and reliable all-solid-state filter scheme was integrated in a two-stage picosecond Nd:YAG regenerative amplifier seeded with pJ-energy femtosecond pulses of the Yb:KGW oscillator, and allowed us to reduce the ASE intensity level down to 1.5×10−8 with reference to the intensity of main 100 ps and 100 μJ pulse.

Evaluation of terrain effect on microwave radiometer measurement and its correction

We develop a new technique for terrain correction of coarse resolution satellite microwave radiometer measurements using the high-resolution digital elevation model (DEM). With the high-resolution DEM and a facet model, we first simulated the terrain influences that resulted from both effects of local incidence and polarization rotation (PR) on the microwave radiometer measurements at the different scales of the radiometer footprints. The emissivity signals of bare surfaces are more sensitive on incidence and PR than vegetated surfaces. So the emissivities at different incidence angles of the bare surface generated by the advanced integral equation model (AIEM) were used to simulate the terrain effects on the satellite measurements. It was found that (1) the PR effect at the satellite footprint can be corrected using the absolute mean PR angle from all facets within the footprint, and (2) the satellite measurements can be described as from a mean incidence angle. Both angles can be obtained from all facets within the footprint with the high-resolution DEM and the satellite viewing geometry. Therefore, a corresponding terrain-correction technique was developed for satellite brightness temperature measurements. We also demonstrate the terrain effects on the satellite measurements from the advanced microwave scanning radiometer–earth observing system (EOS) (AMSR-E).

Polarization Attraction in Counterpropagating Fiber Raman Amplifiers

Polarization attraction in counterpropagating, randomly birefringent, fiber Raman amplifiers is numerically investigated, including the effects of nonlinear polarization rotation, pump depletion and orthogonal Raman gain. The analysis determines the limitations of the pulling efficiency, and shows that the maximum achievable mean degree of polarization is a function of the mean gain.

Coexistence of unequal pulses in a normal dispersion fiber laser

We experimentally demonstrate unequal pulses delivered from an erbium-doped fiber (EDF) laser with net-normal dispersion. Two types of pulses with different durations, energies, and spectra coexist in the same ring cavity. The output spectrum exhibits a broadband base that corresponds to the main pulse and a small rectangular lump that corresponds to the additional satellite pulse. With the enhancement of pump power, the intensity of main pulse almost keeps unchanged while the satellite pulse nearly increases linearly. Based on experimental results, it is indicated that two different pulse shaping mechanisms coexist in laser cavity, where the nonlinear polarization rotation (NPR) and spectral filtering (SF) effect contribute to the formation of main pulse and satellite pulse, respectively.

30 ps pulses source based on a fiber-coupled passively Q-switched microchip laser

We report the design of low-cost and compact short-pulse source based on a fiber-coupled Q-switched microchip laser. The combination of stimulated Raman scattering and nonlinear polarization rotation effects in the fiber associated with appropriate filtering makes it possible to tune pulse duration down to 32 ps with peak power above 3 kW. Pulse to pulse peak power fluctuation is below 4%.

Tunable and Switchable Multiwavelength Passively Mode-Locked Fiber Laser Based on SESAM and Inline Birefringence Comb Filter

A tunable and switchable multiwavelength passively mode-locked fiber laser by using a semiconductor saturable absorber mirror (SESAM) and an inline birefringence fiber filter is proposed and demonstrated. By properly rotating the polarization controllers (PCs), up to 7-wavelength mode-locked pulses in 3-dB bandwidth with 3.65-nm channel spacing are obtained. The wavelength switchable operation is determined by the characteristics of the comb filter used in the experiment. Taking advantage of an intensity-dependent loss mechanism caused by the nonlinear polarization rotation (NPR) effect, the mode competition is efficiently suppressed. In addition, the lasing locations of multiwavelength mode-locked pulses can be flexibly tuned via the wavelength-dependent loss mechanism.

基于单个半导体光放大器的非线性偏振旋转效应实现全光可重构多逻辑门

We demonstrate an all-optical reconfigurable logic gate based on dominant nonlinear polarization rotation accompanied with cross-gain modulation effect in a single semiconductor optical amplifier (SOA). Five logic functions, including NOT, OR, NOR, AND, and NAND, are realized using 10-Gb/s on-off keying signals with flexible wavelength tunability. The operation principle is explained in detail. By adjusting polarization controllers, multiple logic functions corresponding to different input polarization states are separately achieved using a single SOA with high flexibility.

基于单个半导体光放大器的非线性偏振旋转效应实现全光可重构多逻辑门

基于单个半导体光放大器的非线性偏振旋转效应实现全光可重构多逻辑门

All-optical reconfigurable multi-logic gates based on nonlinear polarization rotation effect in a single SOA

All-optical reconfigurable multi-logic gates based on nonlinear polarization rotation effect in a single SOA

Switchable and tunable dual-wavelength ultrashort pulse generation in a passively mode-locked erbium-doped fiber ring laser

A simple switchable and tunable dual-wavelength passively mode-locked erbium-doped fiber ring laser based on nonlinear polarization rotation (NPR) effect is proposed and experimentally demonstrated. The NPR effect effectively induces wavelength- and intensity-dependent loss to readily implement stable dual-wavelength passively mode-locked operation. The wavelength switching and tuning of the dual-wavelength ultrashort pulse laser are achieved only by appropriately rotating the polarization controllers. The side-mode suppression ratio of the output pulse is larger than 41 dB over a wavelength-tuning range of 43.4 nm. Moreover, triple-wavelength ultrashort pulse can also be observed.

All-Optical Signal Processing Based on Nonlinear Effects in Semiconductor Optical Amplifiers

In this paper, we report our recent studies on developing nonlinear techniques based on a single SOA for all-optical signal processing at high-speed, with a focus on simple configurations employing commercial SOAs for several key all-optical network applications. Our researches are based on nonlinear polarization rotation (NPR), four-wave mixing (FWM) and cross-phase modulation (XPM) effects in a single SOA. We propose and demonstrate applications of the nonlinear techniques in all-optical logic gates, multi-function format coversion, tunable Lyot birefringent filter and multi-channel optical time division multiplexed (OTDM) demultiplexing.

Four-channel reconfigurable optical add-drop multiplexer based on photonic wire waveguide

We designed and fabricated a four-channel reconfigurable optical add-drop multiplexer based on silicon photonic wire waveguide controlled through thermo-optic effect. The effective footprint of the device is about 1000 x 500 microm(2). The minimum insertion loss is about 10.7 dB and the tuning bandwidth about 17 nm. The average tuning power efficiency is about 6.187 mW/nm and the tuning speed about 24.4 kHz. The thermo-optic polarization-rotation effect is firstly reported in this paper.

Mechanism of the large polarization rotation effect in the all-dielectric artificially chiral nanogratings

The physical mechanism of the large polarization rotation effect in direct transmission of the all-dielectric artificially chiral nanogratings is explored by experiment and numerical analysis. It is shown that the different coupling of right- and left-circularly polarized components of the normally incident light to the leaky guided modes or Fabry-Pérot resonance modes lead to the enhanced circular dichroism, resulting in the giant polarization rotation effect. The mode profile and local field calculations demonstrate intuitive images of the different coupling performance at resonances.

Matrix-Based Polarization Analysis and Application of Semiconductor Optical Amplifiers

Employing the Mueller matrix method with polar decomposition, we analyse the polarization rotation (PR) effects in semiconductor optical amplifiers (SOAs) and demonstrate that the PR angle is linear to the birefringence dependent gain while the average PR coefficient is about 0.625 for the employed SOA. It is further evident that the current and optical intensity dependent PRs rotate reversely around the same axis. Thus we propose an optical-electric synchronous control scheme to obtain orthogonal polarization states with power-equalization, and implement it by a polarization-sensitive SOA. The polarization duration time is about 10 ns which is applicable to high-speed polarization state generation.

A Tunable Lyot Birefringent Filter With Variable Channel Spacing and Wavelength Using Nonlinear Polarization Rotation in an SOA

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We experimentally demonstrate a tunable fiber-optical Lyot birefringent comb filter with independent tuning of the channel spacing and wavelength. The filter configuration is based on sandwiching a fiber-optic programmable differential group delay line (DGDL) and a semiconductor optical amplifier (SOA) between two polarizers. The channel spacing of the filter can be tuned by adjusting the programmable DGDL. Using the nonlinear polarization rotation effect in the SOA, the phase shift between the transverse electric and the transverse magnetic components of the input probe beam can be adjusted by varying the power of the pump light, and hence fast and continuously wavelength tuning of the filter can also be achieved. The wavelength tuning range is up to 50% of the channel spacing when the pump power is increased from <emphasis><formula formulatype="inline"><tex>${-}$</tex></formula></emphasis>10 to 17 dBm. </para>

Passively Q‐switched erbium‐doped fiber laser based on nonlinear polarization rotation

AbstractWe have experimentally demonstrated an all‐fiber passively Q‐switched Erbium‐doped fiber (EDF) ring laser based on nonlinear polarization rotation. By incorporating a long section of single‐mode fiber and a polarization‐dependent isolator into the EDF ring laser, the intensity‐dependent transmission due to the effect of nonlinear polarization rotation can be implemented, which can act as an artificial saturable absorber for Q‐switching. Such a passively Q‐switched ring laser has the simple and all‐fiber configuration. In addition, passively harmonic mode‐locking and chaotic pulses are also generated from the EDF ring laser. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 694–696, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23185

基于非线性偏振旋转效应的多波长光纤激光器

Multiwavelength fiber laser is a perfect light source for future wavelength-division-multiplexing optical communication systems. A multiwavelength fiber laser based on nonlinear polarization rotation with up to 18 wavelengths has been proposed and demonstrated. The intensity- and wavelength-dependent loss induced by nonlinear polarization rotation effect is used to alleviate the mode competition in the homogeneous broadening gain medium of erbium-doped fiber. Instead of traditional filters, a polarization-maintaining fiber is inserted into the laser cavity, with which the polarization-dependent isolator composes an equivalent Lyot birefringent fiber filter. The in-line birefringence fiber filter is used to simplify the laser configuration, which benefits systematic integration. The effect of the 980 nm pump power on the multiwavelength generation is investigated. It is shown that the pump power contributes a lot to the evenness of the multiwavelength spectra due to the intensity dependence of nonlinear polarization rotation effect.

Analysis of Light Modulation in the Fringe-Field Switching Liquid Crystal Mode

The light modulation mechanism in conventional liquid crystal displays (LCDs) presents either phase retardation or polarization rotation effects only. However, in the fringe-field switching (FFS) mode, both effects exist depending on the electrode positions when the electrode width and distance is larger than 2 μm. Interestingly, when the electrode width and distance are reduced to less than 2 μm, only the polarization rotation effect exists. Further, reduction of the electrode width and distance gives rise to improved response time and light efficiency in the FFS mode.