Figure - available from: Optics Express
This content is subject to copyright. Terms and conditions apply.
OV sidebands topological charge measurement using a tilted lens. Row a (b, c), AS1 (2, 3) are the OVs before the lens, after the lens and interference with a Gaussian reference beam.
Source publication
We have generated multi-color optical vortices in a Raman-active crystal PbWO4 using two-color Fourier-transform limited femtosecond laser pulses. This setup overcomes some of the limitation of our previous research by allowing for the production of subcycle femtosecond optical vortices without the need for compensating for added chirp. In addition...
Similar publications
We propose a new orbital angular momentum (OAM) erbium-doped fiber amplifier based on a circular photonic crystal fiber, which can support a total of 18 modes (14 OAM modes) over C-band. A correction factor is proposed to modify the overlap factor, with the aim of evaluating the performance of the amplifier more accurately. We found that the confin...
The general analytical formula for the propagation of the power-exponent-phase vortex (PEPV) beam through a paraxial ABCD optical system is derived. On that basis the evolution of the intensity distribution of such a beam in free space and the focusing system is investigated. In addition, some experiments are carried out, which verify the theoretic...
We theoretically study a Gaussian optical beam with an embedded off-axis optical vortex. We also experimentally generate such an asymmetric Gaussian optical vortex by using an off-axis spiral phase plate. It is shown that depending on the shift distance the laser beam has the form of a crescent, which is rotated upon propagation. An analytical expr...
Perfect optical vortices (POVs) are beams whose topological charges are independent of radius, unlike conventional optical vortices. POVs are the Fourier transformation of Bessel–Gaussian (BG) beams and can be seen in the far-field diffraction of BG beams. In this paper, we present the generation of POVs of arbitrary charge using curved fork gratin...
Recent studies have reported a new method for the determination of the azimuthal index (topological charge) ℓ of an optical vortex beam (eg. Optics Express 19, 5760-5771 (2011)). Here we consider the performance of such a system for determining both the azimuthal as well as radial indices of a Laguerre-Gaussian beam by measuring the far-field diffr...
Citations
... As an approach to generating vortex laser beams with wavelength diversity, nonlinear optical processes have been investigated. These processes include second harmonic generation (SHG) [21][22][23][24], sum frequency generation (SFG) [25][26], optical parametric oscillation (OPO) [27][28][29][30][31][32][33][34], and stimulated Raman scattering (SRS) [35][36]. In particular, OPO enable not only wavelength conversion, but also offers a unique means by which the OAM of a vortex field can be selectively transferred between the pump, idler and signal fields. ...
... This configuration is achieved by crossing the pump and Stokes input beams at a specific angle inside the crystal [20]. As a result, the generated sidebands are produced at different output angles, and therefore, additional techniques are required to recombine these sidebands and synthesize ultrashort pulses [22][23][24]. In this work, we apply a novel scheme to generate and characterize a few-cycle pulse in a single polychromatic beam. ...
In this paper, we implement a scheme to combine six coherent, spatially separated Raman sidebands generated in single-crystal diamond into a collinear beam. With appropriate phase tuning, this results in a pulse much shorter than the generating pump. We elucidate the characteristics of the synthesized pulse by using an interferometric collinear cross-correlation frequency-resolved optical gating setup. The beating of the synchronized sidebands results in an additional component in the signal, which we use to optimize the relative phases of our sidebands. In this way, we synthesize and measure visible-range, nearly single-cycle isolated pulses of approximately 5-fs total pulse duration.
... This configuration is achieved by crossing the pump and Stokes input beams at a specific angle inside the crystal [20]. As a result, the generated sidebands are produced at different output angles, and therefore, additional techniques are required to recombine these sidebands and synthesize ultrashort pulses [22][23][24]. In this work, we apply a novel scheme to generate and characterize a few-cycle pulse in a single polychromatic beam. ...
In this work, we implement a scheme to combine six coherent, spatially separated Raman sidebands generated in single-crystal diamond into a collinear beam. With appropriate phase tuning, this results in a pulse much shorter than the generating pump. We elucidate the characteristics of the synthesized pulse by using a interferometric collinear cross-correlation frequency-resolved optical gating setup (ix-FROG). The beating of the synchronized sidebands results in an additional component in the signal, which we use to optimize the relative phases of our sidebands. In this way, we synthesize and measure visible-range, near-single cycle isolated pulses of approximately 5 fs total pulse duration.
... Kung and colleagues have demonstrated the synthesis of nonsinusoidal waveforms using molecular modulation [13], and other recent advances using this technique are listed in Refs. [14][15][16][17]. Broadening the spectrum of a femtosecond laser using molecules was first proposed by Kien et al. [18], and was later experimentally demonstrated using Q-switched pulsed lasers by Marangos and coworkers [19]. ...
We describe a new method to broaden the frequency spectrum of a femtosecond oscillator in the continuous-wave (CW) domain. The method relies on modulating the femtosecond laser using four-wave mixing inside a Raman-based optical modulator. We prepare the modulator by placing deuterium molecules inside a high-finesse cavity and driving their fundamental vibrational transition using intense pump and Stokes lasers that are locked to the cavity modes. With the molecules prepared, any laser within the optical region of the spectrum can pass through the system and be modulated in a single pass. This constitutes a CW optical modulator at a frequency of 90 THz with a steady-state single-pass efficiency of ∼ 10 − 6 and transient (10 μs-time-scale) single-pass efficiency of ∼ 10 − 4 . Using our modulator, we broaden the initial Ti:sapphire spectrum centered at 800 nm and produce upshifted and downshifted sidebands centered at wavelengths of 650 nm and 1.04 μm, respectively.
... Optical vortices are of use for studying OAM in nonlinear processes, such as second harmonic generation [2] or broadband Raman generation [3]. Application of optical vortices to broadband coherent Raman generation (otherwise known as 'molecular modulation') provides a way toward spatio-temporal engineering of ultrafast optical fields [4]. ...
... The detection of the resulting mixed OAM modes is generally thought to require sophisticated interferometric techniques [3]. We have proposed a simple experimental setup to study the cleanliness of generated OAM modes, as shown in Fig. 1B. ...
Orbital angular momentum (OAM) transfer through nonlinear processes such as coherent Raman generation often distorts the original spatial mode of light, resulting in OAM superposition states. We characterize such modes and quantify their distortion by astigmatic focusing of the laser beam.
... Wavelength conversion of vortex laser beams is achieved using the same methods used to convert Gaussian laser beams, and here both second order and third order nonlinear wavelength conversion has been demonstrated. Second order processes including sum-frequency generation and second harmonic generation [45], and optical parametric down-conversion of optical vortices [46] have been demonstrated, along with third order stimulated Raman scattering (SRS) [47]. What is interesting to note is that both conservation of energy and momentum must be observed in these nonlinear processes, and this results in quite interesting sharing of the topological charge (associated with OAM) of the vortex beams involved in the nonlinear process. ...
... More recently, within the context of pulsed vortex laser outputs, Zhi et al investigated the interaction of femtosecond optical vortex pulses in a Raman active PbWO 4 crystal [47,90], in which the pump and first-Stokes pulses with specified topological charges of ℓ ℓ and , p s respectively, interacted to generate cascaded higher-order Stokes (S) and anti-Stokes (AS) pulses. In this case, the topological charges, ℓ , n AS and ℓ , n S for the nth-order AS and S pulses should be predicted theoretically as follows: generated from a femtosecond laser system formed of a Ti: sapphire laser, regenerate amplifier, an optical parametric amplifier, and a frequency doubler. ...
The unique properties of optical vortex beams, in particular their spiral wavefront, have resulted in the emergence of a wide range of unique applications for this type of laser output. These applications include optical tweezing, free space optical communications, microfabrication, environmental optics, and astrophysics. However, much like the laser in its infancy, the adaptation of this type of laser output requires a diversity of wavelengths. We report on recent progress on development of optical vortex laser sources and in particular, focus on their wavelength extension, where nonlinear optical processes have been used to generate vortex laser beams with wavelengths which span the ultraviolet to infrared. We show that nonlinear optical conversion can be used to not only diversify the output wavelength of these sources, but can be used to uniquely engineer the wavefront and spatial properties of the laser output.
... Because SLMs and CGHs are phase-only modu- 35 lators, these small distortions can be interpreted as separate components of the beam with different TCs (since TC is the only parameter which characterizes phase). Because nonlinear process amplify small perturbations (noise) [24,25], these extra components play a large role for OVs in different nonlinear processes such as second harmonic generation [26], Raman generation with femtosecond OVs [27,28,29], or white light generation [30]. As a result, the nonlinearly generated beams may become so distorted that they represent a mixed state [31] other. ...
We study the tilted lens technique for measuring the topological charge (TC) of an optical vortex and investigate how this technique works for optical vortices in mixed orbital angular momentum states (i.e. when one beam contains several components with different values of TC). We present experimental results and theoretical simulations for the measurement of the TC of mixed states. We investigate two different cases: when coherent interference (or addition) between components is present and when it is absent (incoherent addition). We discover that this technique is suitable for measuring the TC of the dominant component of a mixed state.
... However, the conventional phase modulation elements typically used to generate optical vortices, such as spiral phase plates and spatial light modulators, are designed for certain wavelengths, so that the frequency of the optical vortices is more or less fixed without any mechanical motion. Nonlinear frequency-conversion techniques, including second-harmonic generation [31][32][33], sum-frequency generation [34,35], optical parametric generation [36,37], and stimulated Raman scattering [38,39], are promising techniques to expand the range of available frequencies for optical vortex sources. ...
We developed an octave-band tunable optical vortex laser based on a 532 nm optical vortex pumped optical parametric oscillator with a simple linear-cavity configuration by employing cascaded non-critical phase-matching LiB3O5 crystals. The optical vortex output was tunable from 735 to 1903 nm. For a pump energy of 9 mJ, an optical vortex pulse energy of 0.24–2.36 mJ was obtained, corresponding to an optical-optical efficiency of 0.3-26%.
... The above listed applications often require wavelength versatility and handedness control of the optical vortices. To date, there have been several demonstrations of wavelength conversion of optical vortices, including second-harmonic generation [18][19][20][21], stimulated Raman scattering [22][23][24], and optical parametric amplification [25]. In particular, moderate energy midinfrared (5-20 μm) optical vortex lasers, which enable the manipulation of eigen-frequencies for numerous molecules, will open the door to a new generation of molecular technologies, such as super-resolution molecular spectroscopy and chiral organic materials processing. ...
We present what is to our knowledge the first demonstration of handedness control of a midinfrared (6.0–12.5 μm) vortex output from a 1 μm vortex-pumped optical parametric oscillator by swapping the frequencies of the signal and idler outputs. Right- and left-handed vortex outputs of over 0.1 mJ were generated within a frequency range of 6.0–11.0 μm. Such a tunable midinfrared vortex laser with handedness selectivity will open the door to chiral organic materials processing.
... Recently a number of investigations involving the nonlinear interaction of optical vortices with matter appeared in the literature [15][16][17]. In experiments presented in [15], the authors crossed time-delayed chirped pulses in a lead tungsten PbWO 4 crystal and demonstrated for the first time the coherent transfer of optical angular momentum in the generation of cascaded Raman sidebands. ...
... In these experiments, topological charge measurements verified a predicted orbital angular momentum algebra (OAM-algebra). This OAM-algebra was later verified in experiments given in [16,17]. In [16] the authors employed two optical parametric amplifiers to produce two spectrally separated beams that were crossed in a Raman active crystal, and in [17] the authors utilized a dichroic beam splitter and spectral filters. ...
... This OAM-algebra was later verified in experiments given in [16,17]. In [16] the authors employed two optical parametric amplifiers to produce two spectrally separated beams that were crossed in a Raman active crystal, and in [17] the authors utilized a dichroic beam splitter and spectral filters. In each of these previous experiments, a spiral phase plate was used producing only the 0, 1 ...
In this work, the nonlinear parametric interaction of optical radiation in various transverse modes in a Raman-active medium is investigated both experimentally and theoretically. Verification of the orbital angular momentum algebra (OAM-algebra) [Strohaber et al., Opt. Lett. 37 , 3411 (2012)] was performed for high-order Laguerre Gaussian modes ℓ > 1 . It was found that this same algebra also describes the coherent transfer of OAM when Ince-Gaussian modes were used. New theoretical considerations extend the OAM-algebra to even and odd Laguerre Gaussian, and Hermite Gaussian beam modes through a change of basis. The results of this work provide details in the spatiotemporal synthesis of custom broadband pulses of radiation from Raman sideband generation.
