Single‐, Dual‐, Triple, and Quadruple‐Wavelength Surface‐Emitting Lasing in Blue‐Phase Liquid Crystal

Abstract

Soft organic lasers with multiwavelength output and high spectral purity are of crucial importance for versatile photonic devices, owing to their monochromaticity, coherence, and high intensity. However, there remain challenges for the achievement of surface‐emitting multiwavelength lasing in soft photonic crystals, and the relative mechanisms need to be investigated. Herein, single‐, dual‐, triple‐, and quadruple‐wavelength lasers are successfully achieved in dye‐doped blue‐phase liquid crystal (BPLC) film. The number and wavelength of the lasing peaks can be manipulated by tuning the center of the bandgap, the order parameter of the laser dye, the quality of the resonance cavity, and even the pump energy. For single‐wavelength lasing, a lasing peak with an ultranarrow linewidth of 0.04 nm (Q‐factor of 13 454) is achieved. Multiwavelength lasing is attained based on the following aspects: i) the narrow bandgaps of the BPLCs with full width at half maximum of 14–20 nm; ii) a laser dye with high gain over a wide wavelength band, having a low‐order parameter in the liquid crystal matrix; iii) appropriate relative positions between the reflection and fluorescence peaks; and iv) the highly ordered crystal lattice of BPLC film. The proposed single‐to‐quadruple‐wavelength surface‐emitting lasers can be employed as coherent light sources for next‐generation optical devices.

Over 200 °C Broad‐Temperature Lasers Reconstructed from a Blue‐Phase Polymer Scaffold

“…[22][23][24][25] Particularly, LC is an ideal candidate for organic optical resonant cavities owing to its self-assembled ordered structures with a tunable photonic bandgap responding to external stimuli. [26][27][28][29][30][31][32][33][34][35][36][37] Blue-phase (BP) liquid crystals (BPLCs) [38][39][40] appeared between the cholesteric (Ch) and isotropic (Iso) states with 3D photonic bandgap, which have superior optical properties [41] for lasers, such as the lower threshold [42,43] and omnidirectional lasing. [44] Therefore, probing light confinement in the BPLCs and using them as novel soft lasers are of great interest.…”

“…Up to now, various BP lasers have been developed based on band-edge lasing, [42,45,46] distributed feedback lasing, [44] defect lasing, [47] and random lasing [48][49][50] using film confined in LC cells [51][52][53][54] or freestanding one. [42,43] Though much progress has been made on BP lasers in terms of the tunability of lasing wavelength under external stimuli, such as light, [55,56] electricity, [45,57,58] temperature, [48,51,54,[59][60][61][62] and mechanics, [63] the research focused on the working temperature of BP lasers is insufficient. Normally, BP lasers operate in a temperature range of 3-4 °C, [54,59] due to the inherent narrow temperature window of BPLCs.…”

Two‐Step Photoalignment with High Resolution for the Alignment of Blue Phase Liquid Crystal

“…[18] The presence of a 3D photonic bandgap (for UV or visible light) makes BPLC an excellent candidate for a wide range of applications in photonic and display devices. [30][31][32][33][34][35][36][37][38][39][40] Therefore, it is significant to explore how the BP crystal structure and alignment can be accurately controlled. Due to the non-uniformity and the short period, it is a challenge to obtain full control of the BP alignment.…”

“…Usually, BPLC is infiltrated in a cell without alignment layers [30] or it is aligned by using a homogeneously oriented layer at the surface, either by rubbing or photoalignment. [33,39,[41][42][43][44] In order to obtain larger domains with homogeneous alignment different procedures have been suggested such as thermal cycling, [45] application of an ac voltage, [36,46] or a gradient-temperature method. [35] Large mono-domains with tailored lattice orientation have also been stabilized by combining weak surface anchoring with appropriate mixture formulations [47] and reconfiguring into stable orthorhombic and tetragonal lattices have been demonstrated with the help of electrical pulses.…”

Scalable Photonic Liquid Crystal Nanoscale-Thick Films for Deformation and Discoloration

“…Though substantial efforts have been made to harness these properties for multi-functional intelligent applications in soft actuators, − displays, lasers, , shape-memory materials, − sensors, , and anti-counterfeiting, the fabrication of three-dimensional (3D) LC elastomers has rarely been investigated yet. Blue phase LCs (BPLCs) are self-assembled 3D photonic crystal materials with nanoperiodic structures and complete photonic band gaps, − corresponding to the structural color in the visible region. In addition, when the periodicity of the crystal lattice is changed by an external field, including the electric field, − temperature, organic gas, , humidity, and other external fields, the reflection color can be changed accordingly.…”