We propose a scheme to generate structured light using a medium consisting of semiconductor quantum dots via four-wave mixing (FWM). We consider a four-level quantum-dot structure where two strong electromagnetic fields couple upper-level biexciton transitions, whereas a weak field is applied to one of the ground-level exciton transitions. A weak signal field is generated, corresponding to a second ground-level exciton transition; thus the overall configuration transforms into a closed-loop diamond-type shape. To realize a spatially dependent modulating quantum-dot medium, we consider strong coupling fields as structured lights and investigate different regions of spatially structured electromagnetically induced transparency via absorption of the generated signal field. The azimuthal phase-dependent modulation of the absorption profile of the generated signal field is the key factor behind the creation of structured light. In addition, we also demonstrate transfer of orbital angular momentum (OAM) of the control beam to the generated beam through the FWM process and study the effect of phase mismatch on efficiency of the OAM transfer.

Spatially structured transparency and transfer of optical vortices via four-wave mixing in a quantum-dot nanostructure

We propose a scheme to demonstrate spatiotemporal-vortex four-wave mixing (FWM) in an asymmetric semiconductor double quantum-well nanostructure. It is found that the orbital-angular-momentum (OAM) phase is transferred entirely from a unique OAM mode to the FWM field. Interestingly, by adjusting the detuning or the intensity of a control field, one can effectively modulate the phase and intensity of the FWM field. Also, we perform the superposition modes created by the interference between the FWM field and a same-frequency Laguerre-Gaussian mode, which show many interesting properties. Moreover, the conversion efficiency and quality of the output FWM field are studied. It is shown that the generated FWM mode has a maximum fidelity of approximately 100%. Our result may find potential applications in fundamental research and quantum technologies based on OAM light in solids.

Efficient spatiotemporal-vortex four-wave mixing in a semiconductor nanostructure

We investigate the interaction of laser pulses carrying orbital angular momentum (OAM) with a symmetry-broken ladder-type quantum coupling scheme involving three internal states. A weak probe beam acts on the lower leg of the ladder scheme, while a control beam of higher intensity drives the upper leg. In contrast to natural atoms, such a model with broken symmetry allows generating a sum-frequency signal beam between the most upper and lower quantum states, forming a cyclic closed-loop configuration of light-matter interaction. We propose situations for the efficient transfer of optical vortices to the generated signal beam via a nonlinear three-wave mixing process. It is demonstrated that the exchange process can occur both in the electromagnetically induced transparency (EIT) and the Autler-Townes splitting (ATS) regimes. The transition between the EIT and ATS conversion schemes can smoothly happen by simply tuning the knob of the control field. It is shown that the ATS regime is considerably more favorable than the EIT to achieve maximum energy conversion efficiency between light beams carrying the OAM. The results may provide an applications-based perspective to the ongoing research centered on vortex conversion-based comparisons between the ATS and EIT.

Exchange of optical vortices in symmetry-broken quantum systems

We propose a theoretical scheme for creating a two-dimensional Electromagnetically Induced Grating in a three-level $$\Lambda $$
 -type atomic system interacting with a weak probe field and two simultaneous position-dependent coupling fields—a two dimensional standing wave and an optical vortex beam. Upon derivation of the Maxwell wave equation, describing the dynamic response of the probe light in the atomic medium, we perform numerical calculations of the amplitude, phase modulations and Fraunhofer diffraction pattern of the probe field under different system parameters. We show that due to the azimuthal modulation of the Laguerre–Gaussian field, a two-dimensional asymmetric grating is observed, giving an increase of the zeroth and high orders of diffraction, thus transferring the probe energy to the high orders of direction. The asymmetry is especially seen in the case of combining a resonant probe with an off-resonant standing wave coupling and optical vortex fields. Unlike in previously reported asymmetric diffraction gratings for PT symmetric structures, the parity time symmetric structure is not necessary for the asymmetric diffraction grating presented here. The asymmetry is due to the constructive and destructive interference between the amplitude and phase modulations of the grating system, resulting in complete blocking of the diffracted photons at negative or positive angles, due to the coupling of the vortex beam. A detailed analysis of the probe field energy transfer to different orders of diffraction in the case of off-resonant standing wave coupling field proves the possibility of direct control over the performance of the grating.

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Azimuthal modulation of electromagnetically induced grating using structured light.

We propose a scheme to demonstrate the manipulation of space-dependent four-wave mixing (FWM) in a four-level atomic system. By adjusting the detuning of the control field, one can effectively control the FWM output field transferred from a pump beam carrying orbital angular momentum. More interestingly, by appropriate choice of the intensity of the control field, the FWM field can be significantly enhanced and phase twist is almost completely suppressed. Furthermore, the superposition modes created by the interference between the FWM field and a same-frequency Gaussian beam are also discussed, showing many interesting properties. Our results may open some possibilities for phase imprinting in Bose-Einstein condensates or atom manipulation with optical tweezers.

Control of space-dependent four-wave mixing in a four-level atomic system

We propose a scheme to generate spatially dependent four-wave mixing (FWM) in an asymmetric semiconductor three-coupled-quantum-well nanostructure. By adjusting the detuning of the control field, one can effectively manipulate the FWM output field. Specifically, the vortex phase of the FWM field can be modulated. The detailed explanations based on the dispersion relation are given, which are in good agreement with our results. Furthermore, we perform the interference between the FWM field and the same-frequency Gaussian beam. Our results show that the interference patterns can also be modulated via the detuning of the control field, which may provide a way to observe helical phase modulation via the intensity measurement. This work may be useful for investigating the nonlinear optical phenomena based on orbital angular momentum light.

Spatially dependent four-wave mixing in semiconductor quantum wells

Orbital angular momentum (OAM) is an important property of vortex light, which provides a valuable tool to manipulate the light-matter interaction in the study of classical and quantum optics. Here we propose a scheme to generate vortex light fields via four-wave mixing (FWM) in asymmetric semiconductor quantum wells. By tailoring the probe-field and control-field detunings, we can effectively manipulate the helical phase and intensity of the FWM field. Particularly, when probe field and control field have identical detuning, we find that both the absorption and phase twist of the generated FWM field are significantly suppressed. Consequently, the highly efficient vortex FWM is realized, where the maximum conversion efficiency reaches around 50%. Our study provides a tool to transfer vortex wavefronts from input to output fields in an efficient way, which may find potential applications in solid-state quantum optics and quantum information processing.

Highly efficient vortex four-wave mixing in asymmetric semiconductor quantum wells.

We propose a new scheme for generating new structured beams via spatially dependent transparency in a three-level atomic system. Due to the joint quantum interference induced by Laguerre–Gaussian (LG) field and constant coupling field, we can achieve different spatially dependent beams by measuring the probe absorption intensity profiles. The proposed scheme may provide potential applications in optics and novel quantum technologies.

Jing Qiu

Papers

Control of space-dependent four-wave mixing in a four-level atomic system

Spatially dependent four-wave mixing in semiconductor quantum wells

Highly efficient vortex four-wave mixing in asymmetric semiconductor quantum wells.

Generation of new structured beams via spatially dependent transparency