Negative-Index Metamaterials: Second-Harmonic Generation, Manley-Rowe Relations and Parametric Amplification

Second harmonic generation and optical parametric amplification in negative-index metamaterials (NIMs) are studied. The opposite directions of the wave vector and the Poynting vector in NIMs results in a "backward" phase-matching condition, causing significant changes in the Manley-Rowe relations and spatial distributions of the coupled field intensities. It is shown that absorption in NIMs can be compensated by backward optical parametric amplification. The possibility of distributed-feedback parametric oscillation with no cavity has been demonstrated. The feasibility of the generation of entangled pairs of left- and right-handed counter-propagating photons is discussed.Comment: 7 pages, 6 figure

Taming optical parametric amplification

Due to a limited number of known laser media technically relevant femtosecond laser systems are restricted to a few laser frequencies only. Tunability based on these sources is enabled by the process of optical parametric amplification (OPA). A small portion of the laser output is used to generate a seed pulse. To enable tunability over a large spectral range a bulk continuum is used. With a strong pump pulse a selected spectral part can be amplified in a suitable nonlinear medium. In order to obtain highly stable and ultrashort pulses on the 10 fs scale a deep understanding of each individual step in the process is necessary. In this work Ti:sapphire and Yb-based laser systems are used to pump OPAs. In the used topology it is possible to utilize repetition rates from 1 kHz to 1 MHz and input energies from 10 to 300 µJ without major changes of the design. We obtain ultrashort pulses from the UV to the MIR. New aspects on bulk continuum generation are presented. For generation with 1030 nm light various crystals are compared regarding the visible and near infrared continuum side. The hitherto unconsidered GSO is found to be superior. Self-compression due to continuum generation is shown without the need for external compression. It bases on a 1 mm sapphire or YAG plate and an astigmatism-free, achromatic telescope . a Schiefspiegler. The self-compressed, unchirped continuum is used to seed a NOPA (noncollinear OPA) for ultra-broadband pulse generation. With this system quantum efficiencies of up to 45% in the amplification process and 18 µJ output are demonstrated and compression down to 6.7 fs. The transmitted seed light after optical parametric amplification and the amplified output can propagate in significantly different directions. This is explained as a consequence of Kerr lensing at the needed pump intensities. A pump induced Kerr lens is acting on the signal/seed pulse. This induces a deflection in the amplifier medium at imperfect input coupling. Locating the amplifier crystal behind the focal plane of the pump minimizes the self-lensing effect due to nonlinear balancing of the beam divergence. This also allows reducing the pump intensity simply by moving the crystal further away from the focal plane. For MHz repetition rates serious thermal issues in a NOPA arise due to the high average power that is needed for the nonlinear processes. For third harmonic generation (THG) of an Yb-fiber laser, second harmonic generation (SHG) with subsequent sum-frequency mixing is demonstrated. Two-photon absorption of the UV leads to measureable heat in the THG crystal. The phase-matching conditions change and the UV power decreases over time. With a time delay compensation plate (aBBO) between the SHG and THG crystal this effect can be minimized. By temporally pre-compensating the fundamental with respect to the second harmonic, the generation locus of the main UV power is shifted to the end of the THG crystal and the volume for absorption is minimized. Stable UV pulses result. This enables a long term stable UV pumped NOPA output even at 1 MHz repetition rate. An OPA for the generation of an octave spanning middle infrared pulse centered around 8 µm is presented. A 515 nm pumped NOPA with a subsequent collinear, 1030 nm pumped amplifier based on LGS is utilized. The chirp management is entirely by bulk material and selected optical filters. The MIR field is temporally characterized by electro-optical sampling. As gate pulse the self-compressed fundamental is used in an extremely simple setup. Electro-optical sampling reveals a compression down to 1.4 cycles of the MIR field and an intrinsically phase-locked CEP stability of better than 94 mrad over one hour

Taming optical parametric amplification

Due to a limited number of known laser media technically relevant femtosecond laser systems are restricted to a few laser frequencies only. Tunability based on these sources is enabled by the process of optical parametric amplification (OPA). A small portion of the laser output is used to generate a seed pulse. To enable tunability over a large spectral range a bulk continuum is used. With a strong pump pulse a selected spectral part can be amplified in a suitable nonlinear medium. In order to obtain highly stable and ultrashort pulses on the 10 fs scale a deep understanding of each individual step in the process is necessary. In this work Ti:sapphire and Yb-based laser systems are used to pump OPAs. In the used topology it is possible to utilize repetition rates from 1 kHz to 1 MHz and input energies from 10 to 300 µJ without major changes of the design. We obtain ultrashort pulses from the UV to the MIR. New aspects on bulk continuum generation are presented. For generation with 1030 nm light various crystals are compared regarding the visible and near infrared continuum side. The hitherto unconsidered GSO is found to be superior. Self-compression due to continuum generation is shown without the need for external compression. It bases on a 1 mm sapphire or YAG plate and an astigmatism-free, achromatic telescope . a Schiefspiegler. The self-compressed, unchirped continuum is used to seed a NOPA (noncollinear OPA) for ultra-broadband pulse generation. With this system quantum efficiencies of up to 45% in the amplification process and 18 µJ output are demonstrated and compression down to 6.7 fs. The transmitted seed light after optical parametric amplification and the amplified output can propagate in significantly different directions. This is explained as a consequence of Kerr lensing at the needed pump intensities. A pump induced Kerr lens is acting on the signal/seed pulse. This induces a deflection in the amplifier medium at imperfect input coupling. Locating the amplifier crystal behind the focal plane of the pump minimizes the self-lensing effect due to nonlinear balancing of the beam divergence. This also allows reducing the pump intensity simply by moving the crystal further away from the focal plane. For MHz repetition rates serious thermal issues in a NOPA arise due to the high average power that is needed for the nonlinear processes. For third harmonic generation (THG) of an Yb-fiber laser, second harmonic generation (SHG) with subsequent sum-frequency mixing is demonstrated. Two-photon absorption of the UV leads to measureable heat in the THG crystal. The phase-matching conditions change and the UV power decreases over time. With a time delay compensation plate (aBBO) between the SHG and THG crystal this effect can be minimized. By temporally pre-compensating the fundamental with respect to the second harmonic, the generation locus of the main UV power is shifted to the end of the THG crystal and the volume for absorption is minimized. Stable UV pulses result. This enables a long term stable UV pumped NOPA output even at 1 MHz repetition rate. An OPA for the generation of an octave spanning middle infrared pulse centered around 8 µm is presented. A 515 nm pumped NOPA with a subsequent collinear, 1030 nm pumped amplifier based on LGS is utilized. The chirp management is entirely by bulk material and selected optical filters. The MIR field is temporally characterized by electro-optical sampling. As gate pulse the self-compressed fundamental is used in an extremely simple setup. Electro-optical sampling reveals a compression down to 1.4 cycles of the MIR field and an intrinsically phase-locked CEP stability of better than 94 mrad over one hour

Optical parametric amplification and oscillation assisted by low-frequency stimulated emission

Optical parametric amplification/oscillation provide a powerful tool for coherent light generation in spectral regions inaccessible to lasers. Parametric gain is based on a frequency {\it down-conversion} process, and thus it can not be realized for signal waves at a frequency $\omega_3$ {\it higher} than the frequency of the pump wave $\omega_1$. In this work we suggest a route toward the realization of {\it up-conversion} optical parametric amplification and oscillation, i.e. amplification of the signal wave by a coherent pump wave of lower frequency, assisted by stimulated emission of the auxiliary idler wave. When the signal field is resonated in an optical cavity, parametric oscillation is obtained. Design parameters for the observation of up-conversion optical parametric oscillation at $\lambda_3=465$ nm are given for a periodically-poled lithium-niobate (PPLN) crystal doped with Nd$^{3+}$ ions.Comment: 6 pages, 5 figures, to appear in Optics Letter

Polarization control for slow and fast light in fiber optical, Raman-assisted, parametric amplification

Efficient slow and fast light fiber devices based on narrow band optical parametric amplification require a strict polarization control of the waves involved in the interaction. The use of high birefringence and spun fibers is studied theoretically, possible impairments evaluated, and design parameters determined.Comment: 20 pages, 7 figures, preprint submitted to Comptes Rendue

Entanglement, EPR correlations and mesoscopic quantum superposition by the high-gain quantum injected parametric amplification

We investigate the multiparticle quantum superposition and the persistence of multipartite entanglement of the quantum superposition generated by the quantum injected high-gain optical parametric amplification of a single photon. The physical configuration based on the optimal universal quantum cloning has been adopted to investigate how the entanglement and the quantum coherence of the system persists for large values of the nonlinear parametric gain g.Comment: 9 pages, 5 figure

Dualism between Optical and Difference Parametric Amplification

Breaking the symmetry in a coupled wave system can result in unusual amplification behavior. In the case of difference parametric amplification the resonant pump frequency is equal to the difference, instead of the sum, frequency of the normal modes. We show that sign reversal in the symmetry relation of parametric coupling give rise to difference parametric amplification as a dual of optical parametric amplification. For optical systems, our result can potentially be used for efficient XUV amplification