We present the one-dimensional optical-waveguiding crystal dithieno[3,2-a:2',3'-c]phenazine with ah igh aspect ratio,high mechanical flexibility,and selective self-absorbance of the blue part of its fluorescence (FL). While macrocrystals exhibit elasticity,m icrocrystals deposited at ag lass surface behave more like plastic crystals due to significant surface adherence,m aking them suitable for constructing photonic circuits via micromechanical operation with an atomic-forcemicroscopyc antilever tip.T he flexible crystalline waveguides displayoptical-path-dependent FL signals at the output termini in both straight and bent configurations,m aking them appropriate for wavelength-division multiplexing technologies. Ar econfigurable 2 2-directional coupler fabricated via micromanipulation by combining two arc-shaped crystals splits the optical signal via evanescent coupling and delivers the signals at two output terminals with different splitting ratios. The presented mechanical micromanipulation technique could also be effectively extended to other flexible crystals.

Precise mechanical processing of optical microcrystals involves complex microscale operations viz. moving, bending, lifting, and cutting of crystals. Some of these mechanical operations can be implemented by applying mechanical force at specific points of the crystal to fabricate advanced crystalline optical junctions. Mechanically compliant flexible optical crystals are ideal candidates for the designing of such microoptical junctions. A vapor‐phase growth of naturally bent optical waveguiding crystals of 1,4‐bis(2‐cyanophenylethynyl)benzene (1) on a surface forming different optical junctions is presented. In the solid‐state, molecule 1 interacts with its neighbors via CH⋅⋅⋅N hydrogen bonding and π–π stacking. The microcrystals deposited at a glass surface exhibit moderate flexibility due to substantial surface adherence energy. The obtained network crystals also display mechanical compliance when cut precisely with sharp atomic force microscope cantilever tip, making them ideal candidates for building innovative T‐ and Δ‐shaped optical junctions with multiple outputs. The presented micromechanical processing technique can also be effectively used as a tool to fabricate single‐crystal integrated photonic devices and circuits on suitable substrates.

Fabrication of organic photonic integrated circuits (OPICs) greatly relies on crystalline materials with high mechanical flexibility and fluorescence (FL). Realizing an efficient OPIC with multiple photonic functions suitable for practical applications depends on creating complex circuit architectures. The mechanical and optical functions of crystals are susceptible to subtle differences in the molecular packing and, more importantly, the type of intermolecular interactions. Herein, an organic crystal (E)‐1‐(4‐(iodo)phenyl)iminomethyl‐2‐hydroxyl‐naphthalene (IPIN) exhibiting high flexibility under mechanical stress, bright green FL, and selective self‐absorbance of the blue part of its broadband FL signal is reported. IPIN microcrystal transduces its FL effectively even in its bent geometry. The significant crystal‐surface adhesion energy facilitates the micromechanical fabrication of a triply‐bent waveguide using a mechano(crystal)photonic approach, which is later integrated with a singly‐bent waveguide to create a unique OPIC. This futuristic OPIC delivers excitation position‐dependent and direction‐specific long‐pass‐filtered narrowband optical signals with different split ratios.

Organicm icro-heterostructures (MHS) with dual optical emissions are essential to produce miniaturized optical waveguidesf or wavelength divisionm ultiplexing technologies. The bimolecular MHS produced by solutionbased bottom-up self-assembly technique often leads to poor surface smoothness, edge imperfection, defects, and unwanted thin films deposits. Conversely,s equential sublimation technique at ambient pressure facilitates effective integration of a-perylene micro-square with dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl) 4H-pyran (DCM) microrods in an epitaxial manner to produce MHS. The obtained DCM/perylene MHS act as optical waveguides to produce red (l max % 670 nm) or/and yellow (l max % 607 nm) dual optical outputs via an energy transfer mechanism depending upon the heterostructures geometry and optical excitation positions. The presented dualcolor emitting MHS opticalw aveguidesa re essential for the integratedn ano-photonic and optoelectronic device structures.Nano-and micro-scaleo rganic devices tructures are rapidly emerging as an alternative to inorganic ones. [1] Mainly,b ecause of the electronic properties of organic molecules are easily tunable via custom-made synthesis, andv ariousf lexible device structure can be fabricated by either solution-or physical vapor deposition techniques. [1] Direct applications of organic molecule-based materials include solid-state lasers, [2] lightemitting diodes and transistors, [3] photovoltaic cells, [4] and miniaturize photonic devices. [2] The micro-/nano-scale photonic device structures comprise of components such as optical waveguides, [5,6] modulators, [5d] filters, [7] cavities, [8] and lasers. [9] The above-mentioned photonic device structures are futuristic and are vital to the development of photon-based quantum information-processing, communication as well as integratedc ircuits. [10] One of the prime requirements for the implementation [a] V. V. Pradeep, Dr.M.A nnadhasan, Prof. R. Chandrasekar

Highly pure, organic, crystalline materials with nonlinear optical (NLO) properties are in great demand due to their potential to be utilized in miniaturized nanophotonic device applications. Perylene dye is one of the celebrated near‐direct bandgap NLO materials. It crystallizes in two distinctive polymorphic forms (square‐shaped, α, and rhombus‐shaped, β) emitting yellow and green fluorescence, respectively. However, selective access to any one of the polymorphic microcrystals possessing qualities such as smooth‐surface and mirror‐like light‐reflecting sharp edges is a challenging task. On the other hand, these qualities are indispensable for a microcrystal to operate as an optical cavity. Here, a cost‐effective and straightforward, yet promising sublimation technique to grow microscale perylene crystals with the above qualities in a polymorph‐selective manner at ambient pressure is presented. As a result, both polymorphic microcrystals act as whispering gallery mode (WGM) cavities in the linear and notably, NLO regime as well. In agreement with the experiments, finite difference time domain numerical calculations support the WGM‐cavity‐type and also reveal the intricate localization of electric‐field within these cavities. Further, the quadratic dependence of emission intensity as a function of laser power establishes the two‐photon absorption nature of the optical cavities pumped by infrared lasers.