Figure - available from: Nanophotonics
This content is subject to copyright. Terms and conditions apply.
Simulated offset angle and scattering efficiency. (a, b) Offset angle versus additional linear phase gradient in the x-axis and y-axis at different wavelengths. (c, d) Simulated efficiency versus wavelength with different additional linear phase gradients in the x- and y-axis, respectively.
Source publication
Phase-structured light beams carrying orbital angular momentum (OAM) have a wide range of applications ranging from particle trapping to optical communication. Many techniques exist to generate and manipulate such beams but most suffer from bulky configurations. In contrast, silicon photonics enables the integration of various functional components...
Similar publications
On-chip integration of two-dimensional (2D) materials with unique structures and distinctive properties endow integrated devices with new functionalities and improved performance. With a high flexibility in modifying its properties and a strong compatibility with various integrated platforms, graphene oxide (GO) becomes an attractive 2D material fo...
On-chip integration of two-dimensional (2D) materials with unique structures and distinctive properties endow integrated devices with new functionalities and improved performance. With a high flexibility in modifying its properties and a strong compatibility with various integrated platforms, graphene oxide (GO) becomes an attractive 2D material fo...
Citations
... Gratings emitting LG modes have previously been designed for IR wavelengths [50], [10], [31], [51], [52]. Recently, a similar holographic approach was implemented to design gratings emitting focused free-space LG beams [53], but various approximations limit both the accuracy and generality of the design process. Focused emission was strictly in the vertical direction, without direct control of the focused waists, and at focal heights only a few microns above the surface. ...
... In the l = 2 profiles the central vortex splits into two separate singularities. This "null splitting" is a common problem in higher order LG beam generation regardless of platform [54] and has been observed in IR coupling gratings at a comparable scale [10], [53]. It is exacerbated by more stringent fabrication limitations (Fig. 10e), as the necessary truncation brings the peak of initial emission closer to the beam center, where the grating lines are increasingly asymmetric. ...
We present a design methodology for free-space beam-forming with general profiles from grating couplers which avoids the need for numerical optimization, motivated by applications in ion trap physics. We demonstrate its capabilities through a variety of gratings using different wavelengths and waveguide materials, designed for new ion traps with all optics fully integrated, including UV and visible wavelengths. We demonstrate designs for diffraction-limited focusing without restriction on waveguide taper geometry, emission angle, or focus height, as well as focused higher order Hermite-Gaussian and Laguerre-Gaussian beams. Additional investigations examine the influence of grating length and taper angle on beam-forming, indicating the importance of focal shift in apertured beams. The design methodology presented allows for efficient design of beam-forming gratings with the accuracy as well as the flexibility of beam profile and operating wavelength demanded by application in atomic systems.
... Azobenzene materials also facilitate phase modulation by altering the timing or phases of different parts of a light wave. This process is integral to enabling beam shaping, producing structured wavefronts, and navigating light in desired directions in applications such as interference patterns, holography [106], and wavefront shaping within optical communication systems [107]. iii. ...
Orbital angular momentum (OAM) encoding is a promising technique to boost data transmission capacity in optical communications. Most recently, azobenzene films have gained attention as a versatile tool for creating and altering OAM-carrying beams. Unique features of azobenzene films make it possible to control molecular alignment through light-induced isomerization about the azo bond. This feature enables the fabrication of diffractive optical devices such as spiral phase plates and holograms by accurately imprinting a phase profile on the incident light. By forming azobenzene sheets into diffractive optical elements, such as spiral phase plates, one can selectively create OAM-carrying beams. Due to the helical wavefront and phase variation shown by these beams, multiple distinct channels can be encoded within a single optical beam. This can significantly increase the data transmission capacity of optical communication systems with this OAM multiplexing technique. Additionally, holographic optical components made from azobenzene films can be used to build and reconstruct intricate wavefronts. It is possible to create OAM-based holograms by imprinting holographic designs on azobenzene films, which makes it simpler to control and shape optical beams for specific communication requirements. In addition, azobenzene-based materials can then be suitable for integration into optical communication devices because of their reconfigurability, compactness, and infrastructure compatibility, which are the main future perspectives for achieving OAM-based technologies for the next generation, among other factors. In this paper, we see the possible use of azobenzene films in the generation and modification of OAM beams for optical communications through light-induced isomerization. In addition, the potential role of azobenzene films in the development of novel OAM-based devices that paves the way for the realization of high-capacity, OAM-enabled optical communication networks are discussed.
... Structured laser beams are indispensable in such areas as advanced optical trapping and manipulation of nano-and micro-objects in various media, mode division multiplexing (MDM) optical communication systems, quantum communication, optical microscopy, laser material processing, and many others [4][5][6][7][8][9][10][11][12][13][14][15]. The most popular approaches for the shaping of structured light are the use of diffractive optical elements (DOEs), metasurfaces, structured screens, or spatial light modulators (SLMs) [16][17][18][19][20][21][22][23][24][25]. These elements and devices can be used to control individual characteristics of laser beams or to control some of them in parallel-for example, amplitude and phase or phase and polarization. ...
We study the sharp focusing of the input structured light field that has a non-uniform elliptical polarization: the parameters of the ellipse depend on the position in the input plane (we limited ourselves to the dependence only on the angular variable). Two types of non-uniformity were considered. The first type corresponds to the situation when the semi-axes of the polarization ellipse are fixed while the slope of the major semi-axis changes. The second type is determined by the situation when the slope of the major semi-axis of the polarization ellipse is constant, and the ratio between the semi-axis changes (we limited ourselves to the trigonometric dependence of this ratio on the polar angle). Theoretical and numerical calculations show that in the case of the first type of non-uniformity, if the tilt angle is a multiple of the polar angle with an integer coefficient, then the intensity distribution has rotational symmetry, and the energy flow is radially symmetric and has the negative direction near the optical axis. In this second case, the intensity symmetry is not very pronounced, but with an odd dependence of the ratio of the semi-axes of the polarization ellipse, the focused field at each point has a local linear polarization, despite the rather complex form of the input field. In addition, we investigate the distribution of the longitudinal component of the Poynting vector. The obtained results may be used for the formation of focused light fields with the desired distributions of polarization, Poynting vector density, or spin angular momentum density in the field of laser manipulation and laser matter interaction.
... Several design methods have been proposed in the research on on-chip spatial light receivers. Traditional methods, such as grating couplers [17], and subwavelength holographic surface gratings [18], have been employed. However, these methods have limitations in terms of their ability to support multiple modes and achieve high coupling efficiency. ...
Photonic integrated spatial light receivers play a crucial role in free space optical (FSO) communication systems. In this paper, we propose a 4-channel and 6-channel spatial light receiver based on a silicon-on-insulator (SOI) using an inverse design method, respectively. The 4-channel receiver has a square receiving area of 4.4 µm × 4.4 µm, which enables receiving four Hermite-Gaussian modes (HG00, HG01, HG10, and HG02) and converting them into fundamental transverse electric (TE00) modes with insertion losses (ILs) within 1.6∼2.1 dB and mean cross talks (MCTs) less than −16 dB, at a wavelength of 1550 nm. The 3 dB bandwidths of the four HG modes range from 28 nm to 46 nm. Moreover, we explore the impact of fabrication errors, including under/over etching and oxide thickness errors, on the performance of the designed device. Simulation results show that the 4-channel receiver is robust against fabrication errors. The designed 6-channel receiver, featuring a regular hexagon receiving area, is capable of receiving six modes (HG00, HG01, HG10, HG02, HG20, and HG11) with ILs within 2.3∼4.1 dB and MCTs less than −15 dB, at a wavelength of 1550 nm. Additionally, the receiver offers a minimum optical bandwidth of 26 nm.
... Such beams contain a phase factor exp(iℓθ), where ℓ stands for topological charge (TC) and θ for the azimuthal angle [11,12]. Various approaches have been developed to generate OAM beams, such as spiral phase plates (SPP) [13][14][15], spatial light modulators (SLMs) [16][17][18], and the holographic fork gratings [19]. In general, VBs can carry both integer and non-integer values of ℓ, the latter being referred to as fractional vortex beams [20]. ...
Diffraction patterns of optical vortex beams (VBs) by differently shaped apertures are used to determine their topological charge (TC). In this paper, we show by simulations and experiments that diffraction of a Laguerre-Gaussian (LG) beam by intersecting circular apertures can be used to reveal the TC. The presented aperture structure has the advantage of the measurement of fractional TC in addition to the integer, sensitivity to the sign of TC, and low sensitivity to adjusting apertures. Accordingly, in addition to the integer TC up to 8, the fractional TC is measured with a step of 0.1 by two intersecting circular apertures (TICA). By examining a wide range of similarity criteria between the diffraction pattern of the fractional TC and the pattern of the lower integer TC, three metrics for measuring the fractional TC are found. Furthermore, the determination of integer TC up to 6 for three intersecting circular apertures (THICA) is demonstrated.
... Gratings emitting LG modes have previously been designed for IR wavelengths [46], [10], [26], [47], [48]. Recently, a similar holographic approach was implemented to design gratings emitting focused free-space LG beams [49], but various approximations limit both the accuracy and generality of the design process. Focused emission was strictly in the vertical direction, without direct control of the focused waists, and at focal heights only a few microns above the surface. ...
... In the l = 2 profiles the central vortex splits into two separate singularities. This "null splitting" is a common problem in higher order LG beam generation regardless of platform [50], and has been observed in IR coupling gratings at a comparable scale [10], [49]. It is exacerbated by more stringent fabrication limitations (Fig. 10e), as the necessary truncation brings the peak of initial emission closer to the beam center where the grating lines are increasingly asymmetric. ...
We present a design methodology for free-space beam-forming with general profiles from grating couplers which avoids the need for numerical optimization, motivated by applications in ion trap physics. We demonstrate its capabilities through a variety of gratings using different wavelengths and waveguide materials, designed for new ion traps with all optics fully integrated, including UV and visible wavelengths. We demonstrate designs for diffraction-limited focusing without restriction on waveguide taper geometry, emission angle, or focus height, as well as focused higher order Hermite-Gaussian and Laguerre-Gaussian beams. Additional investigations examine the influence of grating length and taper angle on beam-forming, indicating the importance of focal shift in apertured beams. The design methodology presented allows for efficient design of beamforming gratings with the accuracy as well as the flexibility of beam profile and operating wavelength demanded by application in atomic systems.
... The usage of integrated photonics for HD QKD with spatial modes, however, is still in its infancy. To date, researchers proposed different integrated designs for the generation or detection of OAM modes and, more recently, polarization-structured vector modes [34,35] based on, e.g., ring-resonators, metasurfaces, grating or inversedesign structures [36][37][38][39][40][41][42][43]. However, most of these devices are static and thus limited in terms of their accessible modes and/or their implementation for HD QKD has not been considered -partially because required MUB states cannot be prepared/measured. ...
Spatial modes of light have become highly attractive to increase the dimension and, thereby, security and information capacity in quantum key distribution (QKD). So far, only transverse electric field components have been considered, while longitudinal polarization components have remained neglected. Here, we present an approach to include all three spatial dimensions of electric field oscillation in QKD by implementing our tunable, on-a-chip vector beam decoder (VBD). This inversely designed device pioneers the "preparation" and "measurement" of three-dimensionally polarized mutually unbiased basis states for high-dimensional (HD) QKD and paves the way for the integration of HD QKD with spatial modes in multifunctional on-a-chip photonics platforms.
... Various approaches have been developed on the silicon photonic platform to generate free-space emission with tailored phase profiles. One type of approach uses apodized shallow-etched surface gratings [15,16]. Another type of approach is based on monolithic integration of metasurfaces on silicon waveguides [17][18][19][20][21][22][23][24][25]. ...
Chip-scale photonic systems that manipulate free-space emission have recently attracted attention for applications such as free-space optical communications and solid-state LiDAR. Silicon photonics, as a leading platform for chip-scale integration, needs to offer more versatile control of free-space emission. Here we integrate metasurfaces on silicon photonic waveguides to generate free-space emission with controlled phase and amplitude profiles. We demonstrate experimentally structured beams, including a focused Gaussian beam and a Hermite-Gaussian TEM10 beam, as well as holographic image projections. Our approach is monolithic and CMOS-compatible. The simultaneous phase and amplitude control enable more faithful generation of structured beams and speckle-reduced projection of holographic images.
... Likely challenges for future potential deployment of OAM-based systems include the development of compact and cost-effective OAM devices. Generally, the desired functions of integrated OAM emitters/detectors might include the capabilities to (i) tune the mode order of the generated OAM beam, (ii) emit an OAM beam over a broad spectral bandwidth, and (iii) generate multiple coaxial OAM beams [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. ...
... Recently, there has been significant research on designing and fabricating photonic-integrated circuit (PIC) devices to generate OAM beams, thereby advancing the deployment of OAM systems with efficient, cost-effective, and compact technologies [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. There are certain desirable features for integrated OAM devices, including low insertion loss, fast tunability, a large number of modes, efficient mode conversion, and a wide wavelength range [44,67]. ...
... There are certain desirable features for integrated OAM devices, including low insertion loss, fast tunability, a large number of modes, efficient mode conversion, and a wide wavelength range [44,67]. Various novel designs of integrated photonic devices have been utilized for OAM-based communication links (Figure 4), including (a) ring resonator-based OAM emitters/receivers embedding angular grating structures with a periodic modulation of the refractive index in the azimuthal direction, which support OAM beams with tunable OAM orders [21,25,29]; (b) circular phase-array OAM emitters/receivers with multiple circular optical antennas to generated/receiver multiple OAM beams [22,27,28]; and (c) subwavelength optical OAM antenna with a relatively compact and specifically designed metasurface to achieve broadband OAM generation/detection [23,32,33,37,38]. ...
There is growing interest in using multiple multiplexed orthogonal orbital angular momentum (OAM) beams to increase the data capacity of communication systems in different frequency ranges. To help enable future deployment of OAM-based communications, an ecosystem of compact and cost-effective OAM generators and detectors is likely to play an important role. Desired features of such integrated circuits include generating and detecting multiple coaxial OAM beams, tunability of OAM orders, and operation over a wide bandwidth. In this article, we discuss the use of pixel-array–based metasurfaces as OAM transmitters and receivers for mode division multiplexing (MDM) communications in near-infrared (NIR) and terahertz (THz) regimes.
Fluorescence microscopy possesses the advantages of high resolution, high sensitivity, molecular specificity and noninvasiveness, providing an important tool in life science research. The multifocal array and 3D structured light are two kinds of important light fields that are often used in scanning fluorescence microscopy systems and wide-field fluorescence microscopy systems. However, traditional methods for generating multifocal arrays and 3D structured light illumination rely on various bulk optical components, making it challenging to achieve compact optical systems. Besides, generating these two types of illumination typically requires two separate and independent optical systems, hindering the integration of different types of fluorescence microscopy systems. Here, a dielectric metasurface is proposed that can achieve the switching between multifocal arrays and 3D structured light through polarization state modulation, greatly simplifying the illumination optics of fluorescence microscopy systems and facilitating the integration of different types of fluorescence microscopy systems.
