LiNbO3 Electro-optic Modulator Research Articles

Research on Compressed Sensing Spectrometry Based on Electro-Optical Transmittance Coding

To develop fast and integrated spectrometry, we present a new method of compressed sensing spectrometry based on electro-optical transmittance coding. A LiNbO3 electro-optic modulator was applied to a directly compressed measurement code in the spectral dimension. Subsequently, a sequential forward floating selection algorithm was employed to select the coding measurement matrix, and sparsity adaptive matching pursuit was used as a solver algorithm. The principle was analyzed, and the measurement system was built for verification experiments. The experimental results reveal that the spectral reconstruction relative error is in the order of 10−2, and the full width at half maximum of the spectral measurement is as high as 1.2 nm. The spectral resolution can reach approximately 0.4 nm in the visible light band range (0.38–0.78 μm) with 1024 spectral channels. The compressed ratio of the compressed sensing spectrometry is up to 1:29. Furthermore, the spectral signal measurement time is only 0.25 ms. The study demonstrates a novel method, which exhibits high precision, speed, high compressed ratio and hyperspectral resolution.

Fast speed switching response and high modulation signal processing bandwidth through LiNbO3 electro-optic modulators

Abstract This work outlined the fast speed response and high modulation bandwidth through LiNbO3 electro-optic modulators. The refractive index is analyzed to estimate the switching voltage and modulation bandwidth for these modulators. The modulation voltage and data transmission data rates are analyzed and discussed clearly through LiNbO3 electro-optic modulators. The modulator’s performance efficiency is upgraded with the optimum modulator length of 10 mm and its thickness of 2 mm. The proposed modulators are compared with GaAs electrooptic modulators under various electro-optic modulators dimensions at 1300 nm near-infrared region and room temperature.

Cascaded modulator topology for frequency conversion in antenna remoting applications.

A new cascaded modulator structure that has the ability to realize high conversion efficiency microwave frequency downconversion, while at the same time able to overcome two fundamental limitations in the dual-parallel modulator approach, is presented. It is based on utilizing the polarization-dependent modulation efficiency property in LiNbO3 electro-optic modulators. The new structure allows the modulators for the RF signal and local oscillator (LO) modulation to be placed in different locations suitable for antenna remoting applications, and it has infinite isolation between the LO and RF signal ports. We present experimental results demonstrating that the proposed structure can be used to realize high conversion efficiency frequency downconversion over wide RF and intermediate frequency (IF) signal frequency ranges as the reported dual-parallel-modulator-based microwave photonic frequency downconverter. Very high isolation of more than 70dB between the LO and RF signal ports is also demonstrated.

Experimental demonstration of optical single sideband signal generation based on multi-frequency phase modulation in optical fibers

We theoretically analyzed and experimentally demonstrated the feasibility of optical single sideband (OSSB) signal generation based on multi-frequency phase modulation. The numerically calculated results show that OSSB signal can be efficiently generated with the proposed method. Optical carrier suppression ratio (OCSR), optical sideband suppression ratio (OSSR) and energy efficiency (EF) of the modulated optical signal increase with the quantity of harmonic waves in the modulation signal. In a principle verifying experiment, 6 frequency phase modulation was carried out with a narrow line-width fiber laser and a LiNbO3 electro-optic phase modulator. The fundamental frequency of the modulation signal was controlled to 30 MHz. OCSR of 18.9 dB, OSSR of 14.1 dB and EF of 78% were obtained, respectively. The experimental results agree well with the numerically calculated results. The proposed scheme provides an effective way to generate an OSSB signal for optical communication or optical sensing systems.

Broadband Photonic Microwave Signal Processor With Frequency Up/Down Conversion and Phase Shifting Capability

A new dual-function photonic microwave signal processing structure that has the ability to realize both frequency up/down conversion and RF/IF phase shifting, is presented. In the proposed signal processor, a dual-polarization dual-parallel Mach Zehnder modulator (DP-DPMZM) is used to generate an orthogonally polarized single RF/IF signal and local oscillator (LO) modulation sideband without an optical carrier. The optical phase difference between the two sidebands can be controlled by controlling a DC voltage applied to a LiNbO3 electro-optic phase modulator that is connected after the DP-DPMZM. Beating between the two sidebands at a photodetector generates an RF/IF signal with a phase equal to the optical phase difference between the IF/RF signal and LO sidebands. The dual-function photonic microwave signal processor has a wide bandwidth and does not require a precise control of the laser wavelength. Experimental results demonstrate that a flat >−3 dB down/up conversion efficiency is achieved for an RF signal from 3.5 to 26.5 GHz and for an IF signal from 0.5 to 3 GHz, and a full 360° continuous phase shift of the output IF/RF signal.

Live Streaming of Uncompressed HD and 4K Videos Using Terahertz Wireless Links

Taming the Terahertz waves (100 GHz–10 THz) is considered the next frontier in wireless communications. While components for the ultra-high bandwidth Terahertz wireless communications were in rapid development over the past several years, however, their commercial availability is still lacking. Nevertheless, as we demonstrate in this paper, due to recent advances in the microwave and infrared photonics hardware, it is now possible to assemble a high-performance hybrid THz communication system for real-life applications. As an example, in this paper, we present the design and performance evaluation of the photonics-based Terahertz wireless communication system for the transmission of uncompressed 4K video feed that is built using all commercially available system components. In particular, two independent tunable lasers operating in the infrared C-band are used as a source for generating the Terahertz carrier wave using frequency difference generation in a photomixer. One of the IR laser beams carries the data which is intensity modulated using the LiNbO3 electro-optic modulator. A zero bias Schottky diode is used as the detector and demodulator of the data stream followed by the high-gain and low-noise pre-amplifier. The Terahertz carrier frequency is fixed at 138 GHz and the system is characterized by measuring the bit error rate for the pseudo random bit sequences at 5.5 Gbps. By optimizing the link geometry and decision parameters, an error-free ( $\text {BER} ) transmission at a link distance of 1 m is achieved. Finally, we detail the integration of a professional 4K camera into the THz communication link and demonstrate live streaming of the uncompressed HD and 4K video followed by the analysis of link quality.

低驱动、高调制X-Cut铌酸锂电光调制器的优化设计

低驱动、高调制X-Cut铌酸锂电光调制器的优化设计

946 nm Nd: YAG double Q-switched laser based on monolayer WSe2 saturable absorber.

In this paper, we report a 946nm double Q-switched laser side pumped by an 808-nm pulse laser diode (LD). A layered tungsten diselenide (WSe2) saturable absorber (SA) together with an MgO doped LiNbO3 electro-optic (EO) modulator is applied to double Q-switch the Nd: YAG laser, producing trains of nanosecond-duration pulses with 500 Hz repetition rate. Such WSe2 saturable absorbers are fabricated by chemical vapor deposition (CVD) in a hot wall chamber and then embedded into a resonant mirror. The achieved pulse energy of double Q-switched laser at 946 nm is approximately 2.63 mJ with 10.8 ns pulse width and the peak power is round 244 kW, corresponding to the beam quality factors of M2x = 3.846,M2y = 3.861. Monolayer WSe2 nanosheets applied in the experiment would be a promising SA for passive Q-switching operation.

Subharmonic synchronously intracavity pumped picosecond optical parametric oscillator for intracavity phase interferometry

The laser system suitable for precise intracavity phase interferometry is presented. The system is based on an intracavity pumped PPLN linear optical parametrical oscillator (OPO). For synchronous pumping of OPO a SESAM-mode-locked, picosecond, diode-pumped Nd:YVO4 linear oscillator, operating at 1.06 µm was used. The OPO cavity was set to be twice as long as the pumping Nd:YVO4 laser cavity. The pumping laser was set in such a manner that the parametric gain inside the PPLN overcame the OPO threshold only for one direction of pumping pulse propagation. This leads to the generation of two independent trains of pulses at the 1.5 µm spectral range. To verify the system performance, a LiNbO3 electro-optic phase modulator was placed inside the OPO. The RF-signal derived from the pumping pulse train, detected by a fast photodiode and divided by two, was applied on the modulator. A stable beat-note signal between the two OPO trains was successfully measured for the first time from such a compact, all-diode-pumped laser system. For RF-signal amplitude from 100 up to 700 mV beat-note frequency varied from 232 up to 1847 Hz which corresponded to detected phase-shift 36–250 µrad. The bandwidth of beat-note was less than 1 Hz (FWHM) resulting in phase-shift measurement error 1.5 × 10−7 rad.

Hybrid silicon and lithium niobate electro-optical ring modulator

Of all oxides, lithium niobate (LiNbO3) is the gold standard electro-optical material in fiber-optic transmission systems. Modulators based on diffused waveguides in bulk LiNbO3 substrates are, however, relatively large. In contrast, ring modulators based on silicon-on-insulator are of interest for chip-scale electro-optical modulation, but unstrained crystalline silicon does not exhibit a linear electro-optic effect, so modulation is based on alternative mechanisms such as the plasma dispersion effect. Here, we present a hybrid silicon and LiNbO3 electro-optical ring modulator operating at gigahertz frequencies. The modulator consists of a 15 μm radius silicon microring and an ion-sliced LiNbO3 thin film bonded together via benzocyclobutene. Fabricated devices operating in the TE optical mode exhibit an optical loaded quality factor of 14,000 and a resonance tuning of 3.3 pm/V. The small-signal electrical-to-optical 3 dB bandwidth is measured to be 5 GHz. Digital modulation with an extinction ratio greater than 3 dB is demonstrated up to 9 Gb/s. High-speed and low-tuning-power chip-scale modulators that exploit the high-index contrast of silicon with the second-order susceptibility of LiNbO3 are envisioned.

Thermally insensitive design for the LiNbO3 electro-optical modulator under dynamic electric field

The electro-optical crystals exhibit thermally insensitive optic propagation orientations, which satisfy the demand of outdoor industry and military applications. With the aid of wave coupling theory, the temperature stability of the LiNbO3 modulator under dynamic electric field is studied and dynamic thermal insensitive (TI) propagating orientation is sought. It is found that a number of propagation orientations have a dramatically different temperature property when the electric field is varied significantly. The temperature drift of light intensity in specific static TI orientation is raise by 3 orders of magnitude. While for dynamic TI orientation, the effect of the electric field is very limited and the temperature drift of modulated intensity can be controlled below 0.3%. The change of electric field orientation does not influence the temperature characteristics of dynamic TI orientation. An effective method is developed to find the thermally insensitive orientations. And the method is suitable for any type of electro-optic crystal with an applied electric field along arbitrary directions.

Birefringence Polarimeter Using Dual LiNbO3 Electrooptic Crystal Modulators

A birefringence polarimeter that uses dual LiNbO3 electrooptic crystal modulators operating at a frequency ratio of 4:1 is described. The significance of this polarimeter is that the birefringent parameters of a sample are obtained only from the modulated polarization status. The measurement, therefore, avoids depolarization effects resulting from the sample itself and the rest of the optical system. The high speed and accuracy of this polarimeter are shown by measurements using a quarter-wave plate, a Babinet–Soleil compensator, and a phase modulator.

Nonlinear resonance phenomena of a doped fibre laser under cavity-loss modulation: Experimental demonstrations

Our experiments with an erbium-doped fibre ring laser (CW, single transverse mode and multiaxial mode) with an intracavity LiNbO3 electro-optic modulator (EOM ) display the characteristic features of a nonlinear oscillator (e.g., harmonic and period-2 sub-harmonic resonances ) when the EOM driver voltage is modulated periodically. Harmonic resonance leads to period-1 bistability and hysteresis. Inside the period-2 sub-harmonic resonance region, the laser exhibits Feigenbaum sequence and generalized bistability.

Electromagnetic field sensor using Mach‐Zehnder waveguide modulator

AbstractAn electromagnetic field sensor linking a LiNbO3 electrooptical modulator with a circular antenna was studied. In this sensor, a Mach‐Zehnder electrooptical modulator was used as one of the fundamental building blocks. The frequency response was flat from 50 MHz to 3 GHz. The minimum detectable electromagnetic field intensity is 0.7 mV/m at 50 MHz and 1.2 mV/m at 3 GHz, respectively. © 2006 Wiley Periodicals,Inc.Microwave Opt Technol Lett 48:1897–1899, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21776

Compensation of self-phase modulation in fiber-based chirped-pulse amplification systems

We demonstrate a simple, all-fiber technique for removing nonlinear phase due to self-phase modulation in fiber-based chirped-pulse amplification (CPA) systems. Using a LiNbO3 electro-optic phase modulator to emulate a negative nonlinear index of refraction, we are able to remove 1.0 pi rad of self-phase modulation acquired by pulses during amplification and eliminate nearly all pulse distortion. Our technique is high speed, removes nonlinear phase on a pulse-to-pulse basis, and can be readily integrated into existing CPA systems.

Broadband and low-driving-power LiNbO3electrooptic modulators

Microwave and optical properties of lithium niobate electrooptic modulators are investigated in this paper. The effect of simultaneous matching of optical and microwave velocities and impedance matching, conductor loss, dielectric loss on the optical bandwidth of an ultra-high-speed lithium niobate modulator are presented here. The metal electrode design, buffer thickness, ridge depth, and the gap between electrodes at different operating frequencies on device performance are thoroughly investigated by using the finite element method.

Narrow-band phase noise measurement around an electro-optically applied, RF phase modulation of a laser field

Light from a monolithic Nd:YAG non-planar ring oscillator laser was phase modulated using a low-phase-noise 12 MHz crystal oscillator driving a LiNbO3 electro-optic modulator. An upper limit to the additional amplitude spectral density of phase noise arising from the modulation process was measured to be 4×10-8 rad/(Hz)1/2 over an 800 Hz bandwidth around the modulation frequency. This noise is in addition to the intrinsic phase noise of the oscillator. This is significantly less than that required by the GEO 600 gravitational wave detector.

100 W average power at 0.53 μm by external frequency conversion of an electro-optically Q-switched diode-pumped power oscillator

We have generated approximately 100 W of frequency doubled light from the output of an electro-optically Q-switched diode-pumped Nd:YAG slab laser oscillator operating at an average power of 200 W (2.5 kHz repetition rate, 80 mJ/pulse, 30 ns pulsewidth). The Q-switch was a compensated z-axis propagation LiNbO3 electro-optic modulator, and the frequency conversion crystal was a thin slab of KTP. In addition, Q-switched operation at an average power of approximately 250 W with 26 ns pulsewidths has been demonstrated.

30 GHz picosecond pulse generation from actively mode-locked erbium-doped fibre laser

Ultrafast picosecond optical pulse generation by harmonic mode-locking of an erbium-doped fibre ring laser is successfully demonstrated. A Ti:LiNbO3 electro-optical modulator driven by a 15 GHz RF signal is used as the mode-locker. Transform-limited pulses with a duration of 7.6 ps arc achieved at a repetition rate of 30 GHz.

40 GHz electro-optic modulator with 7.5 V drive voltage

A wideband, low drive voltage LiNbO3 electro-optic modulator is demonstrated utilising electrodes patterned according to a 13-bit Barker sequence. It exhibits a 3.5 dB optical insertion loss and a 7.5 V switching voltage. The modulation frequency response remains ≥ −5 dB (optical) to beyond 40 GHz.