Frequency Up-conversion Scheme Research Articles

Energy-transfer controlled dual-wavelength visible laser generation based on parallel nonlinear frequency up-conversions

A compact frequency up-conversion scheme is demonstrated for dual-wavelength visible laser generation. The parallel sum-frequency generation (SFG) and second-harmonic generation (SHG) processes are simultaneously phase-matched and integrated in a well-designed periodically poled MgO:LiNbO3 crystal. Concurrent nonlinear up-conversions of the coupled SFG and SHG are thus realized. In the proof-of-principle experiment, two near-IR lasers at wavelengths of 800 nm and 1180 nm were used as independent fundamental beams. As a result, the generation of blue light at ∼477 nm by SFG (800 nm + 1180 nm → 477 nm) and the orange light at ∼590 nm by SHG of 1180 nm (1180 nm + 1180 nm → 590 nm) was simultaneously achieved. Finally, it is proved the relative strength of these two coupled nonlinear interactions and consequently the relative power of the blue and orange light could be freely controlled by changing the pump intensities of the fundamental beams, and a maximum photon conversion efficiency (∼25%) comparable to that of the separated SHG process was observed for this simultaneous dual-up-conversion device. This result provides a promising strategy for developing high-efficiency multi-wavelength visible laser systems. Combined with an engineered QPM crystal with different poling periods in sequence, more prospective nonlinear applications may be realized based a series of cascaded single- and dual-QPM nonlinear processes.

High Linearity Microwave Photonic Up-Conversion System Based on Parallel Dual-Drive Mach–Zehnder Modulators

A large dynamic frequency up-conversion scheme based on parallel dual-drive Mach–Zehnder modulators (DD-MZM) and balance detection is proposed and demonstrated experimentally. By optimizing the distribution ratio of the optical carrier power and the IF signal power between the two DD-MZMs, the third-order intermodulation components in two sub-links cancel each other upon the balanced photodetector. The measured results show that the large spurious-free dynamic range of 112.3 dB·Hz4/5 is obtained for an intermediate frequency signal of 2 GHz up-converted to 18 GHz, which is a 14.8 dB enhancement compared with the traditional carrier suppression double-sideband modulation mixer. The frequency up-conversion performance of the established system for the broadband signal is measured with the results demonstrating the feasibility of the proposed optimization scheme.

Fifth harmonic generation in a medium with cubic nonlinear response based on cascading third harmonic generation

Laser technology has variety of applications for the laser beam and pulse possessing the range of ultraviolet frequencies. Among them, one can emphasise medicine, and semiconductor processing, and material research and many others. To get the light sources in ultraviolet and deep-ultraviolet ranges of frequencies, the frequency conversion processes are often used. One of these processes is the fifth harmonic generation. As a rule, to achieve this, three crystals, possessing quadratic nonlinear response, is used for sequential frequency up-conversion. This way allows us to obtain the energy up-conversion with high efficiency. But, this scheme requires several nonlinear media, which may be sometimes inconvenient, and more important that the quadratic susceptibility restricts the incident pulse intensity.In this paper we propose a new scheme for the fifth harmonic generation basing on the cascading third harmonic generation. This frequency up-conversion scheme requires only one medium with cubic nonlinear response and can be used directly for the pulses with femtosecond duration. Under the big phase mismatching between fundamental wave and the third harmonic, the fifth-order nonlinear response is induced. As well-known, its strength is greater than the own fifth-order susceptibility and it is possible to govern its sign.We demonstrate theoretically its feasibility. Using multi-scale approach, we derive the equations which demonstrate a presence of the fifth-order susceptibility. Based on the problem conservation laws we develop the analytical solution in the frame-work of both long pulse duration approximation and plane wave approximation but without using the non-depletion energy approximation for fundamental wave. This solution allows us to estimate the maximal efficiency of the fifth harmonic generation in dependence of both the self- and cross-modulation of waves and the phase mismatching between fundamental wave and wave of fifth harmonic. Under certain condition it is possible to achieve 93% efficiency of the frequency up-conversion. All results obtained using multi-scale approach are confirmed by the computer simulation results based on nonlinear Schrödinger equations describing the fifth harmonic generation in a medium with cubic nonlinear response.

Tunable Photonic Microwave Up-Converter Using Opto-Electronic Oscillator Based on Monolithic Integrated Three-Section Laser

A tunable photonic microwave frequency up-conversion scheme using opto-electronic oscillator (OEO) based on a monolithic integrated three-section laser without any electro-optic modulator (EOM) or filter is proposed. By adjusting the monolithic integrated three-section laser to operate in the period-one (P1) dynamical state, the signal carrier frequency up-converted from the intermediate frequency (IF) to the frequency at the difference and the summation between the oscillation frequency of OEO and IF can be realized. The tunability of the up-converted frequency can also be greatly guaranteed just by altering the control currents of the monolithic integrated three-section laser induced P1 frequency. In this paper, an IF of 2 GHz with 10 Msymbol/s 16-QAM signals is successfully up-converted to 16 GHz and 20 GHz simultaneously. The up-converted frequencies can be tuned from 16 GHz/20 GHz to 19 GHz/23 GHz, and the error vector magnitudes (EVMs) of all those up-converted signals satisfy the limitation in satellite communication.

Shortening the pulse duration in seeded free-electron lasers by chirped microbunching.

In externally seeded free-electron lasers (FELs) that rely on a frequency upconversion scheme to generate intense short-wavelength light pulses, the slippage effect in the radiator imposes a lower limit on the FEL pulse duration, which is typically on the order of a few tens of femtoseconds. Recently it was proposed that a combination of a chirped microbunch and a tapered undulator can be used to break this limit. Although the method has the potential to reduce the FEL pulse duration down to a level that cannot be achieved by current state-of-the-art technology, it requires a very short seed pulse (∼ one optical cycle or less), making it challenging to put this concept into practical use. Here, we propose an alternative technique to relax the requirement on the seed pulse length. We show that the modified scheme allows generation of FEL pulses with durations much shorter than that determined by the seed pulse and the slippage effect. The performance of the method, which can easily be implemented at existing seeded FEL user facilities, is evaluated through a campaign of analytical calculations and simulations. For our set of typical seeded FEL parameters, we expect the generation of 1.6 fs long pulses at 26 nm with a peak power of 10 GW using a 20 fs long chirped seed pulse operating at 260 nm.

HV discharges triggered by dual- and triple-frequency laser filaments.

We study the use of frequency upconversion schemes of near-IR picosecond laser pulses and compare their ability to guide and trigger electric discharges through filamentation in air. Upconversion, such as Second Harmonic Generation, is favorable for triggering electric discharges for given amount of available laser energy, even taking into account the losses inherent to frequency conversion. We focus on the practical question of optimizing the use of energy from a given available laser system and the potential advantage to use frequency conversion schemes.

Broadband photonic single sideband frequency up-converter based on the cross polarization modulation effect in a semiconductor optical amplifier for radio-over-fiber systems

A broadband photonic single sideband (SSB) frequency up-converter based on the cross polarization modulation (XPolM) effect in a semiconductor optical amplifier (SOA) is proposed and experimentally demonstrated. An optical radio frequency (RF) signal in the form of an optical single sideband (OSSB) is generated by the photonic SSB frequency up-converter to solve the power fading problem caused by fiber chromatic dispersion. The generated OSSB RF signal has almost identical optical carrier power and optical sideband power. This SSB frequency up-conversion scheme shows an almost flat electrical RF power response as a function of the RF frequency in a range from 31 GHz to 75 GHz after 40 km single mode fiber (SMF) transmission. The photonic SSB frequency up-conversion technique shows negligible phase noise degradation. The phase noise of the up-converted RF signal at 49 GHz for an offset of 10 kHz is -93.17 dBc/Hz. Linearity analysis shows that the photonic SSB frequency up-converter has a spurious free dynamic range (SFDR) value of 79.51 dB · Hz(2/3).

Simultaneous Multichannel Photonic Up-Conversion Based on Nonlinear Polarization Rotation of an SOA for Radio-Over-Fiber Systems

A photonic frequency up-conversion scheme based on the nonlinear polarization rotation (NPR) arising in a semiconductor optical amplifier for wavelength-division-multiplexing (WDM) baseband signals is proposed and experimentally demonstrated. Error-free simultaneous up-conversion of 4 times 2.5 Gb/s WDM baseband channels with a 20-GHz local oscillator signal is experimentally demonstrated in the whole C-band. Compared with the cross-gain-modulation-based scheme, the proposed scheme is found to be almost independent of the wavelength separation between the probe and pump signals. Both the radio-frequency spectrum and the bit-error-ratio performance after electrical down-conversion have shown low distortion induced by the optical NPR-based up-conversion.

Photonic Monocycle Pulse Frequency Up-Conversion for Ultrawideband-Over-Fiber Applications

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We demonstrate a photonic monocycle pulse frequency up-conversion scheme for ultrawideband (UWB)- over-fiber applications using nonlinear polarization rotation arising in a semiconductor optical amplifier. For the first time, we have successfully realized the photonic up-conversion of UWB monocycle pulses with an optical local oscillator signal at 24 GHz in the whole <emphasis><formula><tex>$C$</tex> </formula></emphasis>-band. The up-converted UWB monocycle pulse at 24 GHz exhibits a power spectrum density fitting the UWB emission mask. After electrical down-conversion, the UWB monocycle pulse has shown low distortion induced by the optical mixing process. </para>

Second-harmonic generation to the green and yellow using picosecond fiber pump sources and periodically poled waveguides

Compact yellow (560nm) and green (532nm) picosecond pulse sources are demonstrated that utilize second-harmonic generation in periodically poled potassium titanyl phosphate waveguides. Both systems employ ytterbium-doped fiber pump sources. In the yellow case, efficient single-pass Raman scattering in 25m of dispersion-compensating fiber was additionally used to generate the 1.12μm pump. Raman gain could similarly be used in compact configurations to generate other pump wavelengths for use in frequency upconversion schemes.

Multiphoton processes in molecular gases

Abstract The availability of reliable, high-powered, pulsed, tunablc dyc lasers has opened the way to study of a whole host of multiphoton phenomena in molecular gases. This article opens with an overview of the enormous contributions that resonant multiphoton excitation methods are making to our knowledge of the spectroscopy and the dynamics of electronically excited molecules. Another well known class of ‘multiphoton phenomenon’ is exemplified by the various frequency up-conversion schemes now in existence—schemes in which, through use of a suitable nonlinear medium, two or more photons (of the same or different frequencies) may be combined to yield high-energy photons. We conclude this review by considering the potential of molecular gases as nonlinear media for the generation of useful intensities of narrow-bandwidth vacuum-ultraviolet radiation.