From the Cover: Enabling enhanced emission and low-threshold lasing of organic molecules using special Fano resonances of macroscopic photonic crystals

The nature of light interaction with matter can be dramatically altered in optical cavities, often inducing nonclassical behavior. In solid-state systems, excitons need to be spatially incorporated within nanostructured cavities to achieve such behavior. Although fascinating phenomena have been observed with inorganic nanostructures, the incorporation of organic molecules into the typically inorganic cavity is more challenging. Here, we present a unique optofluidic platform comprising organic molecules in solution suspended on a photonic crystal surface, which supports macroscopic Fano resonances and allows strong and tunable interactions with the molecules anywhere along the surface. We develop a theoretical framework of this system and present a rigorous comparison with experimental measurements, showing dramatic spectral and angular enhancement of emission. We then demonstrate that these enhancement mechanisms enable lasing of only a 100-nm thin layer of diluted solution of organic molecules with substantially reduced threshold intensity, which has important implications for organic light-emitting devices and molecular sensing.     

Distinctive signature of indium gallium nitride quantum dot lasing in microdisk cavities

Low-threshold lasers realized within compact, high-quality optical cavities enable a variety of nanophotonics applications. Gallium nitride materials containing indium gallium nitride (InGaN) quantum dots and quantum wells offer an outstanding platform to study light−matter interactions and realize practical devices such as efficient light-emitting diodes and nanolasers. Despite progress in the growth and characterization of InGaN quantum dots, their advantages as the gain medium in low-threshold lasers have not been clearly demonstrated. This work seeks to better understand the reasons for these limitations by focusing on the simpler, limited-mode microdisk cavities, and by carrying out comparisons of lasing dynamics in those cavities using varying gain media including InGaN quantum wells, fragmented quantum wells, and a combination of fragmented quantum wells with quantum dots. For each gain medium, we use the distinctive, high-quality (Q∼5,500) modes of the cavities, and the change in the highest-intensity mode as a function of pump power to better understand the dominant radiative processes. The variations of threshold power and lasing wavelength as a function of gain medium help us identify the possible limitations to lower-threshold lasing with quantum dot active medium. In addition, we have identified a distinctive lasing signature for quantum dot materials, which consistently lase at wavelengths shorter than the peak of the room temperature gain emission. These findings not only provide better understanding of lasing in nitride-based quantum dot cavity systems but also shed insight into the more fundamental issues of light−matter coupling in such systems.The family of III-nitrides materials is promising for the realization of photonic devices including light-emitting diodes and lasers (1–6). These systems have also been explored to engineer quantum emitters based on nitride quantum dots (QDs) that are active at room temperature and are suitable for applications in quantum information science (7). The increased control of the growth of isolated InGaN QDs in a high-quality GaN matrix has also resulted in fabrication of high-quality nitride microcavities including microdisks and photonic crystal cavities with emission at wavelengths in the blue spectral range (320−470 nm) (8, 9). Subsequently, electrically excited emitters and low-threshold lasers based on QDs as the gain medium have been studied (10, 11). However, despite the theoretical advantages of QD lasers, related to the density of electronic states for QDs (12–15), QD microcavity devices still have higher thresholds than quantum well (QW) microcavity devices for the nitride materials (8, 9, 16). Furthermore, InGaN QDs formed through a modified droplet epitaxy (MDE) method are always associated with an accompanying fragmented quantum well (fQW) layer. It is thus important to determine the possible influence of the fQW layer on lasing properties to achieve a better understanding of the unique contribution from the QDs to the lasing mechanism.This work studies the lasing dynamics and the correlation between lasing threshold and lasing wavelength of microdisk lasers whose active areas comprise either QWs, fQWs, or a combination of QDs with fQWs. Through a detailed comparison of lasing in devices with the same geometries but with different active areas, we find that the distinctive signature of QD-facilitated gain is lasing at shorter wavelengths than the average of the background emission. The short wavelength emission is further confirmed by low-temperature, low-power photoluminescence (PL) measurements.     

Single-Mode Lasing in Polymer Circular Gratings

In recent years, conjugated polymers have become the materials of choice to fabricate optoelectronic devices, owing to their properties of high absorbance, high quantum efficiency, and wide luminescence tuning ranges. The efficient feedback mechanism in the concentric ring resonator and its circularly symmetric periodic geometry combined with the broadband photoluminescence spectrum of the conjugated polymer can generate a highly coherent output beam. Here, the detailed design of the ultralow-threshold single-mode circular distributed feedback polymer laser is presented with combined fabrication processes such as electron beam lithography and the spin-coating technique. We observe from the extinction spectra of the circular gratings that the transverse electric mode shows no change with the increase of incident beam angle. The strong enhancement of the conjugated polymer photoluminescence spectra with the circular periodic resonator can reduce the lasing threshold about 19 µJ/cm². A very thin polymer film of about 110 nm is achieved with the spin-coating technique. The thickness of the gain medium can support only the zero-order transverse electric lasing mode. We expect that such a low threshold lasing device can find application in optoelectronic devices.     

Probing the interaction between two single molecules: fluorescence resonance energy transfer between a single donor and a single acceptor.

We extend the sensitivity of fluorescence resonance energy transfer (FRET) to the single molecule level by measuring energy transfer between a single donor fluorophore and a single acceptor fluorophore. Near-field scanning optical microscopy (NSOM) is used to obtain simultaneous dual color images and emission spectra from donor and acceptor fluorophores linked by a short DNA molecule. Photodestruction dynamics of the donor or acceptor are used to determine the presence and efficiency of energy transfer. The classical equations used to measure energy transfer on ensembles of fluorophores are modified for single-molecule measurements. In contrast to ensemble measurements, dynamic events on a molecular scale are observable in single pair FRET measurements because they are not canceled out by random averaging. Monitoring conformational changes, such as rotations and distance changes on a nanometer scale, within single biological macromolecules, may be possible with single pair FRET.     

Luminescence energy transfer using a terbium chelate: improvements on fluorescence energy transfer.

We extend the technique of fluorescence resonance energy transfer (FRET) by introducing a luminescent terbium chelate as a donor and an organic dye, tetramethylrhodamine, as an acceptor. The results are consistent with a Förster theory of energy transfer, provided the appropriate parameters are used. The use of lanthanide donors, in general, and this pair, in particular, has many advantages over more conventional FRET pairs, which rely solely on organic dyes. The distance at which 50% energy transfer occurs is large, 65 A; the donor lifetime is a single exponential and long (millisecond), making lifetime measurements facile and accurate. Uncertainty in the orientation factor, which creates uncertainty in measured distances, is minimized by the donor's multiple electronic transitions and long lifetime. The sensitized emission of the acceptor can be measured with little or no interfering background, yielding a > 25-fold improvements in the signal-to-background ratio over standard donor-acceptor pairs. These improvements are expected to make distances > 100 A measurable via FRET. We also report measurement of the sensitized emission lifetime, a measurement that is completely insensitive to total concentration and incomplete labeling.     

Plasmonically Enhanced Colloidal Quantum Dot/Graphene Doped Polymer Random Lasers

An improvement in random lasers based on a colloidal quantum dot (QD)/graphene-doped polymer was observed and attributed to multiple light-scattering and graphene surface plasmon resonance. The emission characteristics of quantum dots doped with graphene oxide and reduced graphene oxide were compared. The QD/reduced graphene oxide hybrid exhibited a lower laser emission threshold (~460 μJ/cm²). The emission modes and thresholds were strongly dependent on both the graphene doping concentration and the external temperature. Decreased plasmon coupling was the primary reason for lower QD/graphene laser emission with increasing temperature. The optimum reduced graphene oxide concentration was 0.2 wt.%. This work provides a practical approach to optimizing the threshold and stability of random laser devices, with potential applications in displays, sensors, and anti-counterfeiting labels.     

Zinc porphyrin: a fluorescent acceptor in studies of Zn-cytochrome c unfolding by fluorescence resonance energy transfer

FRET between the zinc porphyrin (ZnP) chromophore in zinc-substituted cytochrome c (Zn-cyt c) and an Alexa Fluor dye attached to specific surface sites was used to characterize Zn-cyt c unfolding. The use of ZnP as a fluorescent acceptor eliminates the need to doubly label the protein with exogenous dyes to perform FRET experiments in which both donor and acceptor fluorescence is monitored. The requirement for attachment of only one dye also minimizes perturbation to the protein. This sensitive technique allowed for the determination of distances between the label placed at six different sites and ZnP through a range of denaturant concentrations. Fitting of the data to a three-state model provides distances in the unfolding intermediate. The use of ZnP as a fluorescent acceptor of energy in FRET has a significant potential for application to a range of other systems including heme-binding proteins and proteins to which a covalently attached heme tag may be added.     

Thermal Effects In Vivo from Holmium: YAG Lasing in the Intracoronary Setting

While the thermal effect of laser energy does ablate atheromatous plaque, thermal injury to adjacent tissue produces high rates of arterial thrombosis and spasm. Holmium:YAG lasers use a pulsed laser source to maximize photoblative effects while minimizing thermal effects. These lasers have been utilized clinically to ablate thousands of complex coronary lesions with low rates of spasm and thrombosis, suggesting that little or no thermal injury occurs with these devices. However, we have been able to detect thermal injury in patients angioscopically in coronary arteries after holmium:YAG lasing. Here we report the use of directional coronary atherectomy (DCA) to òbiopsyó arteries in patients following holmium:YAG laser treatment, allowing direct histologic examination of lased tissue. Thirty such lased DCA samples were matched for patient age, gender, target vessel, and lesion characteristics with thirty control DCA samples obtained from patients undergoing DCA without prior lasing. Blinded pathologic examination correctly identified 27/30 control samples but only 18/30 lased samples. Subsequent unblinded analysis, sometimes with recutting and restaining of tissue blocks, resulted in the detection of thermal effects in 27/30 lased samples. The thermal effects seen included edge disruption, charring, coagulation necrosis, and most commonly, vacuolization. We conclude that holmium:YAG lasing does produce detectable thermal effects in tissue in most patients. These effects can be quite subtle or can be extensive, but do not predict poor patient outcome.     

Fragmentation of biliary calculi with tunable dye lasers

The feasibility of using lasers to fragment biliary calculi was examined in vitro. Flashlamp-pumped tunable dye lasers were coupled to small-diameter flexible quartz fibers that were placed in direct contact with biliary calculi. The minimum laser energy necessary to damage a calculus was measured for wavelengths between 450 and 700 nm and for pulse durations between 0.8 and 360 microseconds. This threshold energy increased with increasing wavelength but was not significantly affected by pulse duration. Cholesterol stones had uniformly higher thresholds than pigmented ones. When a repetitively pulsed laser was used, complete fragmentation required fewer than 500 pulses and fragments were predominantly less than 2 mm. The pulsed dye laser can effectively fragment biliary calculi when transmitted through a small-diameter quartz fiber and may be useful as a tool for fragmenting retained common duct stones.     

Mechanism of four-level laser action in solution excimer and excited-state proton-transfer cases

Four-level laser energy level schemes are compared from the mechanistic spectroscopic viewpoint: (i) noble-gas excimer, (ii) solution molecular excimer, (iii) conventional dye laser, and (iv) intramolecular proton transfer. The lasing action of the chlorophyll special pair is discussed as an example of a solution excimer laser, and the lasing action of 3-hydroxyflavone and other molecules is discussed as an example of an intramolecular proton-transfer laser.     

Photoacoustic fibrinolysis: Pulsed-wave, mid-infrared laser-clot interaction

Objectives The purpose of this study was to determine whether a mid-infrared laser can induce selective fibrinolysis and to analyze the effect of altered fibrin structure (thin vs. thick fibers) on laser-clot interaction.Background Mechanical disruption of thrombus can be achieved with balloon angioplasty, sonication, and thermal energy. Thrombi avidly absorb light in the mid-infrared optical spectrum due to their high water content. This phenomenon provides a potential for mid-infrared lasers as a source for selective thrombolysis. As fibrin is the essential component of clot, a study of mid-infrared laser-fibrin interaction is warranted.Methods Clots of varying fibrin structure were lased in cuvettes with a solid-state, pulsed-wave, mid-infrared laser (2.1 micron, 500 mJ/pulse, 250 msec pulse length). Total pulse energies of 5 Joules (J), 10 J, 37.5 J, 75 J, and 112.5 J were tested. Protein content of the extruded fluid was measured by optical density absorbance at 280 nm. The amount of released material was studied as a function of lasing energy and clot structure. SDS-polyacrylamide gel electrophoresis was applied for analysis of protein bands in order to identify unique protein bands released by the selective effect of laser fibrinolysis.Results A threshold for mid-infrared laser induced fibrinolysis was found; application of up to 20 J of energy did not result in dissolution. As lasing energy was increased above 37.5 J, the structure of these gels was mechanically destroyed and 12.4 ± 6.7% (mean ± SEM) of the original content of protein was released. Electrophoresis revealed that lased gels did not release any unique protein band. Lased, thin fibers released significantly less protein than thick fibers, indicating that they are more resistant to the effect of this wavelength of energy.Conclusions Mid-infrared laser can induce in-vitro photoacoustic dissolution of fibrin clots. However, this wave-length laser achieves fibrinolysis by mechanical destruction of the target clot rather than by a selective effect, as induced by the pulsed-dye laser. A threshold exists for energy levels required. Thin fibrin fibers, with their high elastic modulus (i.e., gel rigidity) appear more resistant than thick fibers to the effect of lasing at this wavelength.This work was supported in part by a research grant from Boston Scientific, Boston, MA.     

The Design and Research of a New Hybrid Surface Plasmonic Waveguide Nanolaser

Using the hybrid plasmonic waveguide (HPW) principle as a basis, a new planar symmetric Ag-dielectric-SiO₂ hybrid waveguide structure is designed and applied to nanolasers. First, the effects on the electric field distribution and the characteristic parameters of the waveguide structure of changes in the material, the nanometer radius, and the dielectric layer thickness were studied in detail using the finite element method with COMSOL Multiphysics software. The effects of two different dielectric materials on the HPW were studied. It was found that the waveguide performance could be improved effectively and the mode propagation loss was reduced when graphene was used as the dielectric, with the minimum effective propagation loss reaching 0.025. Second, the gain threshold and the quality factor of a nanolaser based on the proposed hybrid waveguide structure were analyzed. The results showed that the nanolaser has a lasing threshold of 1.76 μm⁻¹ and a quality factor of 109 when using the graphene dielectric. A low-loss, low-threshold laser was realized, and the mode field was constrained by deep sub-wavelength light confinement. This structure has broad future application prospects in the integrated optics field and provides ideas for the development of subminiature photonic devices and high-density integrated circuits.     

Expanded dynamic range of fluorescent indicators for Ca(2+) by circularly permuted yellow fluorescent proteins

Fluorescence resonance energy transfer (FRET) technology has been used to develop genetically encoded fluorescent indicators for various cellular functions. Although most indicators have cyan- and yellow-emitting fluorescent proteins (CFP and YFP) as FRET donor and acceptor, their poor dynamic range often prevents detection of subtle but significant signals. Here, we optimized the relative orientation of the two chromophores in the Ca(2+) indicator, yellow cameleon (YC), by fusing YFP at different angles. We generated circularly permuted YFPs (cpYFPs) that showed efficient maturation and acid stability. One of the cpYFPs incorporated in YC absorbs a great amount of excited energy from CFP in its Ca(2+)-saturated form, thereby increasing the Ca(2+)-dependent change in the ratio of YFP/CFP by nearly 600%. Both in cultured cells and in the nervous system of transgenic mice, the new YC enables visualization of subcellular Ca(2+) dynamics with better spatial and temporal resolution than before. Our study provides an important guide for the development and improvement of indicators using GFP-based FRET.     

FRET-based mapping of calmodulin bound to the RyR1 Ca2+ release channel

Calmodulin (CaM) functions as a regulatory subunit of ryanodine receptor (RyR) channels, modulating channel activity in response to changing [Ca²⁺]_i. To investigate the structural basis of CaM regulation of the RyR1 isoform, we used site-directed labeling of channel regulatory subunits and fluorescence resonance energy transfer (FRET). Donor fluorophore was targeted to the RyR1 cytoplasmic assembly by preincubating sarcoplasmic reticulum membranes with a fluorescent FK506-binding protein (FKBP), and FRET was determined following incubations in the presence of fluorescent CaMs in which acceptor fluorophore was attached within the N lobe, central linker, or C lobe. Results demonstrated strong FRET to acceptors attached within CaM's N lobe, whereas substantially weaker FRET was observed when acceptor was attached within CaM's central linker or C lobe. Surprisingly, Ca²⁺ evoked little change in FRET to any of the 3 CaM domains. Donor–acceptor distances derived from our FRET measurements provide insights into CaM's location and orientation within the RyR1 3D architecture and the conformational switching that underlies CaM regulation of the channel. These results establish a powerful new approach to resolving the structure and function of RyR channels.     

Laser-Tissue Interactions With the Pulsed Dye Laser

The laser-tissue interaction of the pulsed dye laser was assessed. The histological appearance of the craters showed precise margins with no evidence of collateral thermal tissue damage. The ablation of soft yellow atheroma was consistently about two- to threefold that of normal wall, but fibrous white atheroma was resistant to laser energy, and was ablated less than normal wall. The maximum probe tip temperature in air was 197°C, but there was relatively little heating of the coronary artery wall during lasing, and this was minimized by saline perfusion at low flow rates. Lasing produces up to 10¹² irregularly shaped debris particles per liter. Debris from thrombus and normal aorta caused significant platelet aggregation in vitro, but atheromatous debris did not. In conclusion, the characteristics of the pulsed dye laser are suitable for intravascular lasing, but selective ablation of atheroma was not achieved.     

Comparison of tissue disruption caused by excimer and midinfrared lasers in clinical simulation

Laser coronary angioplasty is a useful therapy for selected complex coronary lesions. Laser-induced acoustic trauma is postulated to be a cause of dissection and acute vessel occlusion. Controversy exists regarding the relative degree of photoacoustic effects of midinfrared and excimer lasers in clinical practice. To date, these systems have not been compared at clinical energy doses and with clinical pulsing strategies. Therefore, we studied the photoacoustic effects of both midinfrared and excimer lasing at clinically accepted doses. Human atherosclerotic iliofemoral artery segments were obtained at autopsy (n = 36) and placed lumen side up in a saline bath. Clinical laser catheters were advanced over an 0.018′ guide wire, perpendicular to the tissue. A 10-g down force was applied to the catheter for full-thickness lasing. Pulsing strategies were, for midinfrared laser: 5 pulses, 1-sec pause, 5 pulses, 1-sec pause, 5 pulses, withdraw; for excimer: 5 sec of pulses, wait 10 sec, 5 sec of pulses. Several clinically acceptable energy levels were used; for excimer: 25 mJ/mm², 40 mJ/mm², 60 mJ/mm²; for midinfrared: 3 W (400 mJ/mm²), 3.5 W (467 mJ/mm²). Photoacoustic effect was assessed histologically by determining the number of lateral cleavage planes (dissections) arising from the lased crater border and extending into the surrounding tissue. In normal tissue, midinfrared lasing produced less acoustic damage than excimer lasing (2.79 ± 0.78 vs. 5.27 ± 0.75 cleavage planes, mean ± SD, P < 0.05, data for lowest energy for each system). The same was true in noncalcified atheroma (2.48 ± 0.71 vs. 6.43 ± 1.09, P < 0.05) and calcified atheroma (2.47 ± 1.21 vs. 6.27 ± 1.13, P < 0.05). This effect was similar at all energy levels, with a trend for more damage at higher energies in both systems. This study demonstrates that midinfrared lasing causes less acoustic damage than excimer lasing when using clinical catheters, energy levels, and pulsing strategies. This effect is independent of tissue-type but tends to be dose-related. These findings may explain, in part, the differences in dissection rates seen clinically. © 1996 Wiley-Liss, Inc.     

Ceramic Laser Materials

Ceramic laser materials have come a long way since the first demonstration of lasing in 1964. Improvements in powder synthesis and ceramic sintering as well as novel ideas have led to notable achievements. These include the first Nd:yttrium aluminum garnet (YAG) ceramic laser in 1995, breaking the 1 KW mark in 2002 and then the remarkable demonstration of more than 100 KW output power from a YAG ceramic laser system in 2009. Additional developments have included highly doped microchip lasers, ultrashort pulse lasers, novel materials such as sesquioxides, fluoride ceramic lasers, selenide ceramic lasers in the 2 to 3 μm region, composite ceramic lasers for better thermal management, and single crystal lasers derived from polycrystalline ceramics. This paper highlights some of these notable achievements.     

Cleaved-coupled nanowire lasers

The miniaturization of optoelectronic devices is essential for the continued success of photonic technologies. Nanowires have been identified as potential building blocks that mimic conventional photonic components such as interconnects, waveguides, and optical cavities at the nanoscale. Semiconductor nanowires with high optical gain offer promising solutions for lasers with small footprints and low power consumption. Although much effort has been directed toward controlling their size, shape, and composition, most nanowire lasers currently suffer from emitting at multiple frequencies simultaneously, arising from the longitudinal modes native to simple Fabry–Pérot cavities. Cleaved-coupled cavities, two Fabry–Pérot cavities that are axially coupled through an air gap, are a promising architecture to produce single-frequency emission. The miniaturization of this concept, however, imposes a restriction on the dimensions of the intercavity gaps because severe optical losses are incurred when the cross-sectional dimensions of cavities become comparable to the lasing wavelength. Here we theoretically investigate and experimentally demonstrate spectral manipulation of lasing modes by creating cleaved-coupled cavities in gallium nitride (GaN) nanowires. Lasing operation at a single UV wavelength at room temperature was achieved using nanoscale gaps to create the smallest cleaved-coupled cavities to date. Besides the reduced number of lasing modes, the cleaved-coupled nanowires also operate with a lower threshold gain than that of the individual component nanowires. Good agreement was found between the measured lasing spectra and the predicted spectral modes obtained by simulating optical coupling properties. This agreement between theory and experiment presents design principles to rationally control the lasing modes in cleaved-coupled nanowire lasers.As miniaturized lasers see a rapid increase in applications for digitized communication and signal processing, the monochromaticity of the lasing output becomes an important figure of merit (1). Laser emission at multiple frequencies can lead to both temporal pulse broadening and false signaling because of group-velocity dispersion (2). These problems are avoided by controlling the laser to oscillate at a single frequency. Single-mode lasing is obtained when the spectral spacing between the modes, the free spectral range, is larger than the bandwidth of the optical gain (3–5). Although they are intriguing miniaturized lasers (6–11), individual semiconductor nanowires would need to be as short as a couple of microns to lase at a single optical frequency because of their relatively broad gain profile (>10 nm at room temperature) (12, 13). With the low reflectivity of the end facets (14), such short nanowires are inefficient resonators and may not have a lasing threshold that can be reached with the limited gain of the material (15, 16); with this in mind, coupling nanowire cavities is a promising route to produce single-mode operation. Previous reports of laterally coupled nanowires required micromanipulation to create a coupling structure. This form of evanescent wave coupling is highly sensitive to geometric parameters, such as internanowire distances, lengths of the coupled segments, and perimeters of the nanowire loops (17, 18). The reliance on micromanipulation, with its innate imprecision, limits the control over the coupling properties, introduces surface contamination that alters cavity modes, and restricts the miniaturization of the overall dimension of the devices. An alternative photonic architecture to increase the free spectral range is the radiative coupling of two Fabry–Pérot cavities axially through an air gap, known as the cleaved-coupled cavity (19–22). To achieve this geometry in nanowires, the two cavities can be defined by cutting a single nanowire, which ensures that the two cavities are axially aligned. This approach eliminates the need to position two separate nanowires next to each other with nanoscale precision, a feat that is required by the lateral coupling scheme. However, applying this axial coupling concept to nanowires introduces a new complication: the range of gap widths is limited because diffraction losses at the gap increase with the reduction of the cavity’s cross-sectional dimensions. In this work, we use design principles derived from finite-element method simulations and transfer matrix methods to experimentally demonstrate single-mode lasing in cleaved-coupled nanowires. The modeling and optical measurements show that a gap width smaller than λ/2 is paramount for effective optical coupling, which eliminates the applicability of the rule of λ/2 to cleaved-coupled nanowires (23). A gap at this scale provides the complementary benefits of single-mode lasing at a lower threshold gain than that of the individual component nanowires. Such nanoscale gaps can be defined precisely using readily available fabrication techniques. Because they require no positioning of the nanowires, cleaved-coupled cavities constructed out of single nanowires allow us to achieve reliable and reproducible control of the lasing modes.     

Stability-Enhanced Emission Based on Biophotonic Crystals in Liquid Crystal Random Lasers

A new design of a bio-random laser based on a butterfly wing structure and ITO glass is proposed in this article. Firstly, the butterfly wing structure was integrated in a liquid crystal cell made of ITO glass. The integrated liquid crystal cell was injected with liquid crystal and dye to obtain a bio-random laser. A non-biological random laser was obtained with a capillary glass tube, liquid crystal and dye. The excitation spectra and thresholds were recorded to evaluate the performance of the biological and non-biological random lasers. The results show that the excitation performance stability of the bio-random laser is improved and the number of spikes in the spectra is reduced compared with the non-biological random laser. Finally, the equivalent cavity length of the biological and non-biological random lasers was compared and the optical field distribution inside the butterfly wing structure was analyzed. The data show that the improvement of the excitation performance stability of the bio-random laser is related to the localization of the optical field induced by the photonic crystal structure in the butterfly wing.