Search

We propose and demonstrate a fabrication-friendly on-chip polarizer based on polarization-selective corner mirrors. The total internal reflection angles are distinct between TE and TM modes due to the strong birefringence of silicon-on-insulator (SOI) waveguide. Thus, by properly choosing the inclination angle, TE mode can be completely reflected at each corner mirror with negligible losses, whereas TM mode can be efficiently filtered out. The minimum feature size of such polarizer is as large as 400 nm. The measurement results show low excess losses of 20 dB over a 200-nm bandwidth. Such high performance can be maintained even with a large width deviation of $> \pm 50$ nm.

We propose and numerically investigate the use of birefringent vertical-cavity surface-emitting lasers (VCSELs) under the injection and modulation of spin polarized electrons for application to analog radio over fiber (RoF) systems. Injection current and electron spin polarization in a birefringent VCSEL are individually modulated for generating data signals and a millimeter-wave carrier and a polarizer is used to combine two orthogonal polarizations. A preliminary experiment without spin injections confirms that 24-GHz carrier generation originating from polarization-mode splitting of the birefringent VCSEL can be used for the heterodyne detection of square-wave signals with a period of 6.4 ns. Our findings mark the first step in applying spin-injected birefringent VCSELs having the capability of ultra-high-frequency modulation for application to analog RoF systems.

A compact and high performance integrated silicon TM-pass polarizer is proposed and experimentally demonstrated. The device is formed by periodically structuring a waveguide with a slot section within each period, and is implemented on a silicon-on-insulator platform. The fabricated device has low insertion loss for the TM mode (average 0.7dB) and high extinction for the TE mode (average 41.25dB), over a 1.5 $\mu \text{m}$ to 1.6 $\mu \text{m}$ wavelength range. Numerical simulations indicate that a large fraction of the blocked TE mode radiates out of the periodic structure, resulting in weak back reflections. The compact footprint of the device (21 $\mu \text{m}\,\,\times $ 0.5 $\mu \text{m}$ ) makes it suitable for dense integration in photonic integrated circuits.

A configurable optical waveguide polarizer using graphene oxide (GO) as a polarizing element has been demonstrated. The propagation characteristics of the GO-coated optical waveguide are changed from TM-pass to TE-pass by controlling the GO coating thickness in the sub-micron range during the deposition process. The highest extinction ratio measured for a TM-pass waveguide polarizer is 34.9 dB, using a coating length and thickness of 1.0 mm and $0.34~\mu \text{m}$ respectively, while the highest extinction ratio measured for a TE-pass polarizer is 46.0 dB, using a coating length and thickness of 1.0 mm and $0.71~\mu \text{m}$ respectively. The polarization extinction ratio has also been measured across the wavelength range from 1520 nm to 1620 nm - and a variation of less than 3.0 dB was obtained. Control of the coating thickness dependent characteristics of the GO-coated waveguides provides an avenue for tailoring of the polarization selection.

Wavelength dependence of phase modulators has been one of the main challenges in spectroscopic ellipsometry/polarimetry (EP) which significantly complicates signals analysis. A known approach to overcome this complication is using rotatable polarizers. However, the use of rotatable polarizers induces mechanical vibrations and unnecessary errors to the system. In this work, a novel spectroscopic configuration to extract the spectral changes of the EP parameters applied to surface plasmon resonance (SPR) sensing is presented. The setup utilizes the integration of a recently developed achromatic variable liquid crystal waveplate to the SPR in Kretschmann-Raether configuration and using three phase shifts to extract the EP parameters of the SPR sample.

High polarization extinction ratio (PER) in-fiber polarizers are essential in various fiber-based technologies. In this letter, we propose and demonstrate an in-fiber dispersion compensated polarizer (DCP) based on integrated fiber gratings, which is fabricated by a UV-inscribed 45° tilted fiber grating (TFG) and a chirped fiber Bragg grating (CFBG) in series. Such compact device could enhance the PER of 45° TFG with nearly double value and it is potential to achieve ultra-high PER with relatively short length and simple fabrication. Meanwhile, DCP could also function as a dispersion management component. Finally, with the integrated grating device, we have demonstrated an all fiber mode-locked laser system, generating soliton pulses at the normal and anomalous dispersion regime, respectively.

We report an electro-wetting liquid lens with dual apertures which consists of internal channel with two variable interfaces and external channel with a plano-concave solid lens. And we use LC cell and Polarizers to achieve switching between internal and external channel. The proposed lens can achieve a large turning range of focal length, and the shortest positive and negative focal length are ~24 mm and ~−16 mm, respectively. Meanwhile, the experimental results show that the angular resolution of the proposed lens can reach to $\sim 29^{\prime \prime }$ . It has potential to be applied in cameras, microscopes and so on.

We have proposed a magnetic field sensor using orbital angular momentum (OAM) $ {L}= {\pm }1$ modes, corresponding to right- and left- handed circular polarization, respectively, in a vortex fiber that supports propagation of these modes. These two circularly polarized OAM modes produce a phase difference under the Faraday effect, which results in the rotation of optical petal when both OAM modes pass through a polarizer. A photodetector is used to detect the intensity variation of the output from the polarizer followed by a slit. By using this method, we have experimentally achieved the superposition of OAM modes with the vector representation of HE21 mode for magnetic field sensing. And a magnetic field sensitivity of 3.31%/ $T$ can be reached at the width ratio of the slit to the petal-like pattern of 0.35 ± 0.02. The obtained experimental results prove the successful implementation of this proof-of-concept principle, showing its potential applications in all-fiber current sensing.

A new scheme to improve spurious free dynamic range (SFDR) of high-performance radio over fiber (RoF) link based on 120° phase angle has been proposed and investigated. The proposed link consists of a dual electrode Mach–Zehender modulator (DE-MZM), linear polarizers, and optical filter. The performance is improved by generating an optical single sideband (OSSB) signal using 120° phase angle in DE-MZM. The suppression of third-order intermodulation (IM3) and other harmonics are significantly controlled by adjusting the state of polarization of both the polarizers. The resulting SFDR shows an improvement of 13.4 dB for the proposed linearized link when compared with conventional 90° phase angle-based DE-MZM link.

In this letter, we propose a novel broadband IF-over-fiber transmission system employing a polarization modulator (PolM). PolMs are special phase modulators, which can support both TE and TM modes with opposite phase modulation indices. If a polarizer is placed after the PolM with an angle of 45° to one principal axis of the PolM, then an equivalent intensity modulator (IM) can be achieved. On the other hand, if the direction of the polarizer is parallel to one principal axis of the PolM, an equivalent phase modulator (PM) can be achieved. As a result, we can utilize a PolM to achieve the functions of a parallel IM/PM transmitter, which is previously reported in mobile fronthaul to overcome the dispersion-induced power fading effect. Compared with the conventional parallel IM/PM transmitter based on an IM and a PM, our scheme only needs one modulator, which significantly reduces the cost and avoids the disparity in operation requirements between the IM and the PM. As a demonstration, we successfully transmit $14 \times 1$ GHz OFDM/OQAM signals with a data rate of 44.7 Gb/s over 25 km of a single-mode fiber.

A simple method to produce an all-fiber circular polarization filter is proposed and experimentally demonstrated, which is realized based on the utilization of two consecutively cascaded single-helix helical long-period fiber gratings but with opposite helicities (SHLPGs-OHs). The proposed SHLPGs-OH can be used as a circular polarizer as well as an equivalent half wave-plate, which enables us to turn a left-circular (right-circular) polarization light to a right-circular (left-circular) polarization one. As a concept-proof example, a polarization-converter with an extinction ratio (between the left- and the right-circular polarization light) of ~20 dB, insertion loss of ~10 dB, and a bandwidth of ~4 nm has been successfully demonstrated.

The ability to continuously alter the light transmittance through a window is significant for many optoelectronic devices. However, such versatility usually comes with additional unwanted power consumption. Here, we demonstrate transmittance-tunable glass that operates without electrical power. The key element to the device is an axis-varying polarizer, which combines a photoalignment technique with dichroic dye self-assembly mechanism. By linear translation of one patterned polarizer with respect to the other, different transmittance states can be achieved. Large-scale uniformity and relatively wide viewing angles (±60°) are also demonstrated. Furthermore, low-temperature treatment (i.e., T < 80 °C) during fabrication demonstrates the device’s potential to be made on the plastic substrate. The polarizer with patterned absorption axis can also be used as other optical components such as light amplitude shaping device.

Tunable guided-mode resonance filters (GMRFs) for multi-primary colors based on a twisted nematic liquid crystal (TN-LC) polarization rotator with high peak efficiencies, narrow linewidths, and low sidebands are experimentally demonstrated. The proposed tunable color filter consists of a linear polarizer, the TN-LC polarization rotator, and the GMRF from top to bottom. The polarization of the linear polarized beam generated by the linear polarizer is controlled using a TN-LC. The resonance wavelengths and resonance peaks of the GMRFs are tuned following the orientation of the TN-LC directors. Thus, 3 ~ 6 high saturated primary colors with tunable intensities can be obtained by controlling the applied voltages on the TN-LC of every filter separately.

Fiber-optic linear polarizer (LP) is a key component in measuring the polarization extinction ratio (PER) of integrated optic chip utilizing white light interferometry. Intrinsic structural imperfections in LPs, such as rotation angle deviation, however, can directly impact PER measurement accuracy. In this letter, an improved PER measurement method called orthogonal alignment method is proposed. Based on the traditional PER measurement method, a secondary measurement is carried out by rotating the axis-alignment angles of the polarization-maintaining fiber connection points from 0° to 90°. The PER measurement error induced by LPs can be then removed after calculating the average value of the two measurements. Experimental results indicate that the measurement error can be reduced to 0.02 dB for low-PER (~50 dB) measurement and to 0.1 dB for ultra-high-PER (~90 dB) measurement.

A compact transverse-electric (TE)-pass polarizer for slot waveguides based on an asymmetrical directional coupler is proposed, where a slot waveguide and a linearly tapered waveguide (TW) cascading a hybrid plasmonic waveguide (HPW) are utilized. By properly choosing the structural parameters, the TW is cutoff for TE mode and the phase-matching condition is only satisfied for transverse-magnetic (TM) mode. As a result, the injected TM-mode can be evanescently coupled to the adjacent TW and then attenuated via the HPW while the input TE-mode will directly output, realizing an efficient TE-pass polarizer. With the help of the tapered structures, extinction ratio (ER) is enhanced and fabrication requirements are relaxed. Results show that the proposed polarizer has an ER of 27.1 dB at $1.55~\mu \text{m}$ , and its bandwidth is ~170 nm for an ER > 20 dB and an IL < 0.6 dB. In addition, fabrication tolerances to the key dimensions are analyzed and field evolution is also presented.

A thermally/electrically tunable graphene on white graphene polarizer is proposed, in which the resonant coupling between the plasmonic surface modes of the structure and the transverse electric (TE) [or transverse magnetic (TM)] polarized incident wave is used to absorb this polarization, while the TM (or TE) polarized incident wave is totally reflected. It is then shown that the thermal and electrical tunability of surface conductivity of graphene can be used to control the optical properties of the proposed polarizer, including the selection of the desired polarization, and adjusting the amplitude of the reflected (desired) polarization. The application of the hexagonal boron-nitride (white graphene) as the substrate of graphene increases the propagation of the surface waves of the structure, which in turn results in the very high polarization extinction ratio of 75 dB. Moreover, the ultra-small insertion loss of 0.022 dB and relatively large bandwidth of ~ 60 nm are calculated for the proposed polarizer.

We propose an effective approach to generate tunable orbital angular momentum (OAM) beam based on all-fiber fused coupler consisting of a single mode fiber (SMF) and a two-mode fiber. The fundamental mode in the SMF is directly coupled to the LP11 mode group (TE0,1, $\text {HE}^{\text {even,odd}}_{2,1}$ , TM0,1) by appropriately phase matching the modes in the fiber coupler. The experimental results demonstrate that the OAM beam is produced by combining $\text {HE}^{\text {even}}_{2,1}$ and TE0,1 (or $\text{HE}^{\text {odd}}_{2,1}$ and TM0,1) with a $\pi $ /2 phase shift and the OAM topological charge could be tuned from $l = -1$ to $l =+1$ by adjusting a polarizer set at the output end of fiber.

We propose black-phosphorous (BP) TE- and TM-pass polarizers whose polarization state can be controlled using strong in-plane anisotropic property of BP. The tunable polarizer is configured as a BP-SiO2 metamaterial waveguide to take advantage of the change in refractive index of the whole structure. TE and TM-pass polarizers can be achieved with small footprint ( $20~ \mu \text{m}$ ) and high extinction ratio from 12 to 30 dB for TM-pass polarizer and 17 to 24 dB for TE-pass polarizer. Furthermore, this device exhibits a wide working bandwidth in the visible regime from 500 to 800 nm. Our scheme features simple structure, compact size, and good integrated compatibility, prospecting great potentiality in future optic communications and optical signal processing.

We present a method based on spatial and spectral (S2) imaging technique to measure the vector modal content of vortex fibers. Different vector modes can be told apart and their modal contents can be determined by implementing the S2 imaging process four times with four different polarizer directions. Moreover, the orbital angular momentum modes (OAMs) can be observed directly through the spiral phase patterns without interference process, and the OAM mode purity can be obtained from the intensity and phase patterns.

In this letter, we present a novel and simple method to suppress the signal fading phenomena in polarization optical time-domain reflectometry (POTDR). A combination of polarization multiplexing and multi-directional polarization analyzing is utilized to achieve the goal. A short polarization maintaining fiber is connected to a multi-wavelength laser source to generate polarization multiplexing probe lightwaves. The signals for different probe lightwaves are demultiplexed by a dense wavelength division multiplexer. Then, the three polarizers with different orientations are used to analyze the signals, respectively. The principle of the method is analyzed in detail. Experiments demonstrate the validity of the system to suppress the signal fading. The proposed method can eliminate the location error of event caused by the signal fading and the signal-to-noise ratio is also improved compared with a traditional POTDR.

A compact TE-pass polarizer for silicon wires (SWs) based on a symmetrical three-guide directional coupler (DC) is proposed, where two identical hybrid plasmonic wave-guides (HPWs), including bends are symmetrically located at both sides of the central SW. By properly choosing the structural parameters, the phase-matching condition is only satisfied for TM mode. Therefore, the input TE-mode can directly pass through while the injected TM-mode will be evenly coupled to the adjacent HPWs and attenuated via the HPWs. Consequently, an efficient TE-pass polarizer is realized. With the symmetrical three-guide DC configuration, device length is significantly reduced, and more importantly, an ultralow insertion loss (IL) can be obtained. From the results, the proposed polarizer has an extinction ratio (ER) of 40.8 dB and an IL of 0.09 dB at $1.55~\mu \text{m}$ , and its bandwidth is ~160 nm for an ER > 30 dB dB. In addition, fabrication tolerances to the key structural parameters are analyzed and field evolution through the polarizer is also presented.

An on-chip silicon TE-pass polarizer is proposed and demonstrated. The proposed polarizer is realized by asymmetrical directional couplers assisted with sharp bending and tapered waveguides. The TM0 mode is converted into TM1 mode through the asymmetrical directional coupler and then filtered out by the bending and taper, while TE0 mode goes through with negligible coupling due to the phase mismatch. The measured extinction ratio at central wavelength is 29.8 dB, while the −15 dB bandwidth is >80 nm.

We present a method to generate tunable orbital angular momentum (OAM) based on linearly polarized (LP) modes in optical fibers. The tunable OAM is produced by combining two even (odd) LP modes with orthogonal polarization directions. The tunability of OAM is realized by controlling the power proportion of the two LP modes through a polarizer. From another perspective, the generated mixed vortex can also be regarded as a result of overlapping two orthogonal optical vortices of equal helicity but opposite chirality, then the tunable OAM can be achieved through filtering the mixed mode using a polarizer.

Extremely short length and ultrahigh extinction ratio TE pass polarizer is proposed for wavelength $1.55\mu \text{m}$ . The polarizer section consists of an optical dielectric waveguide separated from the thin metal film plasmonic guide by a low index buffer layer. The thin film metal layer supports only Short Range Surface Plasmon Polariton (SRSPP) because effective indices below and above the metal film are different. Periodic coupling between the SRSPP mode and the optical waveguide mode takes place and varies with the length of the polarizer. It is shown that for a properly optimized metal and the buffer layer thicknesses, an extinction ratio of 223 dB can be achieved for a polarizer of length $4.6~\mu \text{m}$ . Dependence of polarizer length on the optimized buffer and metal layers is also discussed.

Wire grid polarizers (WGPs) are composed of 1-D nanoscale periodic structures and are widely used in liquid crystal display devices to enhance brightness and improve the utilization rate of the backlight source. This letter proposes a new design of a WGPs chip, which can be used in a physical force sensor. In this way, the WGPs can fabricate on many types of microstructure, such as cantilever beam, thin film, and bridge. Then, infrared light was served as the signal source, and illuminated WGPs chip with the optimum angle. When a physical force is applied to the microstructure, the incident angle of infrared light will be varied, resulting in different transmission signal output. As a result, this system can be used for designing the physical force-measuring module operated by optical contactless sensing approach. Furthermore, the WGPs structure introduced in this letter was defined by laser interference lithography and deposited Al by E-beam evaporation.

Polarization topological order of a cylindrical vector beam (CVB) can be defined as the repetition number of 360° polarization state change along the azimuthal axis, with its sign denoting the rotating direction of the polarization. In order to detect CVBs with different order, a miniaturized polymer grating is proposed and demonstrated. The grating is almost pure phase modulated and polarization independent. The CVB modes with different orders or with the same order but opposite sign can easily be separated by adding a quarter wave plate and a polarizer. The experimental results are consistent with the theoretical predictions, thus validating our proposed method.

Active transverse electric and transverse magnetic-pass polarizers with only 1 μm length based on Ge 2 Sb 2 Te 5 (GST) silicon waveguides are theoretically demonstrated. The tunability of both polarizers relies on the phase change of GST. The analysis predicts that both devices exhibit insertion losses (ILs) below 0.8 dB in an amorphous phase. With the change to the crystalline phase, the undesired polarization is attenuated above 18.2 dB, whereas ILs are maintained below 0.8 dB (TM pass) and 2.6 dB (TE pass) at a center wavelength of 1550 nm. The operation bandwidth over a range of 100 nm is also achieved.

A horizontal silicon slot waveguide TE-pass polarizer with thin indium–tin oxide (ITO) layer embedded in the slot region is proposed and investigated. Since the dispersion relation of the material can be tuned by properly adjusting the carrier concentration, ITO is able to act as epsilon-near-zero (ENZ) material with high absorption near 1.55- $\mu \text{m}$ wavelength. With thin ENZ material embedded in the slot waveguide, huge polarization-dependent loss between fundamental TE mode and TM mode can be induced. Therefore, the slot waveguide functions as a TE-pass polarizer with good performance. Our simulation shows that in a 3- $\mu \text{m}$ -long polarizer with 10-nm-thick ITO layer embedded in the slot region, insertion loss of 42 dB for TM mode, and 0.38 dB for TE mode can be achieved simultaneously. The polarizer possesses the advantages of low insertion loss, high extinction ratio, ultra-compact, broadband, and large fabrication tolerance.

We investigated all-optical shift register operations using 1.55-μm polarization bistable vertical-cavity surface-emitting lasers (VCSELs) formed in an array. The VCSEL array consisted of VCSELs that oscillated with single longitudinal and transverse modes at room temperature. The lasing wavelengths were tuned by adjusting the driving currents of each VCSEL. A VCSEL in the array exhibited polarization flip-flop operation by injection of the orthogonally polarized set-reset input pulses. By injection of the VCSEL output light into another VCSEL in the same array through a polarizer and an optical gate, the second VCSEL also exhibited polarization flip-flop operation according to the polarization state of the first VCSEL. The shift register operation has been successfully demonstrated using two adjacent VCSELs in the array. The optical power needed for polarization switching is usually lower than the VCSEL output power. Thus, this shift register operation was achieved without optical amplifiers.

An ultrahigh extinction ratio and extremely short length resonant integrated optic TE pass polarizer are proposed, which is based on the interaction between the short range surface plasmon polaritons and the mode guided by the dielectric waveguide. It is shown that a compact very high extinction ratio and very low insertion loss TE pass polarizer can be designed by optimizing the buffer and metal layer thicknesses. The layer thicknesses and indices are chosen in a way, such that the multilayer plasmonic structure supports only asymmetric eigenmodes. It is shown that, as a result of interference (beat formation) between these asymmetric eigenmodes, a polarizer with an extinction ratio of 171 dB and insertion loss less than 0.01 dB can be designed for 49.4 $\mu \text{m}$ of its length.

TE-pass and TM-pass polarizers based on silicon-on-insulator platform are proposed and analyzed. The suggested structures for both the polarizers are truly CMOS-compatible relying on the titanium nitride as an alternative plasmonic material for its favorable properties. The analysis predicts 0.0635-dB insertion loss (IL) and 20-dB extinction ratio (ER) for the TE-pass polarizer at 3.5- $\mu \text{m}$ active device length. The TM-pass polarizer has an IL of 1 dB and an ER of 20 dB at 2.84- $\mu \text{m}$ -long device, at a central wavelength of 1.55 $\mu \text{m}$ .

A frequency-doubling optoelectronic oscillator (OEO) has been proposed. In the proposed device, several passive components are introduced into the traditional OEO to handle the polarization state of the laser in the feedback loop. Making use of the polarization dependence of the LiNbO3 intensity modulator, a special double sidebands modulation is implemented where the polarization direction of the optical carrier is orthogonal with that of the first-order sidebands. Two polarizers are used to choose the specific optical components from the modulated light, which ensures that a microwave signal at the second-harmonic frequency outputs from the OEO when the fundamental frequency signal is self-oscillating in the loop. In the experiment, a 20-GHz frequency-doubled signal was generated, whose phase noise performance and immunity to the polarization drift were measured and evaluated.

Development of liquid crystal (LC) lenses is limited by the power law. The aperture size of LC lenses is traded for the lens power. In this letter, we prove theoretically and experimentally that the aperture size is not limited by the power law based on a polarizer-free LC lens exploiting an embedded-multilayered structure. By adding numbers of LC layers, the aperture size of the LC lens can be enlarged without lowering the tunable lens power. The optical theory of the polarization independence of the LC lens is derived. The wavefronts are measured after light propagates through the LC lens to discuss the polarization independence and image adjustment. The impact of this study is to show the possibility of LC lenses with large aperture size for wearable devices and ophthalmic applications.

An ultracompact and broadband TE-pass polarizer based on a hybrid plasmonic waveguide is proposed on the silicon-on-insulator platform. The optimized design has an active region as small as $0.8~\mu $ m, which is the shortest polarizer reported until now, and exhibits high polarization-dependent transmission imposing a TM mode cutoff while leaving the TE mode almost unaffected. Finite-difference time-domain simulation reveals an insertion loss

A three-dimensional display system based on metal nano-grating structure is modeled. The aluminum based nano-grating structures are designed and fabricated by nano-imprint as a linear polarizer to select the transverse magnetic wave in the wavelength range of 400–700 nm. The average transmission of the nano-grating for the transverse magnetic wave is around 80% and the polarization ratio of the emission light can reach as high as 97.1%. The polarization characteristics are studied theoretically, simulated by rigorous coupled wave analysis, and verified experimentally in detail.

We report an all-fiber passively mode-locked laser at 1030 nm. The principle of this ultrafast laser is based on nonlinear polarization evolution occurring in a long span of birefringent fiber spliced between a polarizer and a Faraday mirror. This configuration supports a large variety of pulsed regimes: noise-like, multiple pulses, burst, and single pulse mode-lock operation. In the single pulse mode-lock regime, the pulse duration is \(\sim 17.8\) ps at a low repetition rate of 948 kHz. The spectral bandwidth is \(\sim 2.2\) nm, the pulse energy is 68 pJ, and the polarization extinction ratio is estimated to 15 dB.