High-efficiency Laser Research Articles

Hg3P2S8: A New Promising Infrared Nonlinear Optical Material with a Large Second-Harmonic Generation and a High Laser-Induced Damage Threshold

The development of new infrared (IR) nonlinear optical (NLO) materials with strong second-harmonic generation (SHG) responses and high laser-induced damage thresholds (LIDTs) is urgent but challenging. Herein, the defective diamond-like chalcogenide Hg3P2S8 (HPS) was rationally designed and fabricated by a flexible and rigid tetrahedral motif combined strategy. HPS exhibits a phase-matching SHG response of similar to 3.6 x AGS (the largest one in the reported ternary sulfides), high LIDT (similar to 3 x AGS), wide IR transparent region (0.43-16.3 mu m), moderate birefringence (0.043 at 1064 nm), and good physicochemical stability and crystal growth habits. Theoretical analyses confirm that the large SHG effect originates from the synergistic effects between distorted HgS4, PS4, and vacancy-induced nonbonding electrons. The results indicate that HPS is a promising NLO candidate for high-power, high-efficiency laser output in the mid-IR region, which provides an insight into the exploration of new IR NLO materials.

Enhanced IR luminescence properties of Ho3+ ions in oxide glasses modified by the introduction of chloride

Ho3+-doped multifunctional multicomponent glass fibers with effective 2.8 μm emission have attracted significant attention owing to their wide range of applications in various fields over the past decades. However, certain challenges in satisfying the demands of high-efficiency lasers remain to be overcome. In this study, Ho3+ ion single-doped oxide glasses modified by chloride were successfully fabricated and analyzed. The results of the X-ray diffraction (XRD) and differential scanning calorimetry (DSC) indicated the multicomponent glass exhibited better thermal stability and crystallization resistance. The effect of varying chloride content on the structural units of the glass network was carefully analyzed based on the Raman results, indicated that the introduction of chloride can promote the transition of structural units in the glass network environment and lead to a positive impact on the luminescence of Ho3+ ions. Furthermore, the mid-infrared luminescence of Ho3+ was systematically investigated with enhanced luminescence performance under 650 and 1177 nm pumping sources. Hence, these experimental results suggested that Ho3+ doped multicomponent glass can be considered as an attractive candidate medium for high-efficiency laser applications in the infrared region.

Optimization of widely tuneable hybrid erbium-Raman-gain random fibre laser: theoretical investigation

In this study, we investigated the realization of maximum tuning range of a random fibre laser by adjusting the pump wavelength and power as well as changing the lengths of single-mode and erbium-doped fibres (SMF and EDF) to achieve hybrid erbium-Raman gain. With this hybrid gain, the widest tuning range was 90 nm (1524–1614 nm), optimal pump wavelength was 1489 nm, optimal SMF length was 10 km, and optimal EDF length was 15 m. The lasing power flatness is greatly improved with this optimization. Numerical results indicate that the optical conversion efficiency is as high as 71.1%, with a pump power of 2.7 W and an optical signal-to-noise ratio over 55 dB. Hence, this work effectively optimizes and inspires the exploration of and new schemes for broad wavelength tuneable and high-efficiency random fibre lasers.

Heterogeneous Integration of III–V Materials by Direct Wafer Bonding for High-Performance Electronics and Optoelectronics

III-V materials, such as InGaAs and InP, are highly attractive for high-performance electronics and optoelectronics owning to their high carrier mobilities and potential for bandgap engineering. Integration on silicon substrates, however, is a key requirement to enable widespread adoption of these materials. In this work, direct wafer bonding (DWB) of III-V materials is explored as a low-temperature enabling technology for Si integration. For high-performance logic and RF electronics, DWB is compared to competing integration technologies and is shown to exhibit higher device performance due to its relatively low process complexity and thermal impact (~300 °C). Due to the low thermal impact of DWB, it is also uniquely suitable for 3-D integration, i.e., vertical stacking of multiple functional layers. III-V optoelectronics are attractive in such 3-D stacks, where they can enable high-efficiency tunable lasers together with Si photonics integrated circuits. DWB is here compared to selective epitaxy as an integration route for InP-on-Si microdisk lasers. Plasmonics are explored as well, allowing scaling of integrated III-V photonic devices beyond the diffraction limit of light. The results of this work show that DWB is a highly promising integration route for III-V materials for both electronics and optoelectronics applications.

Tailoring the efficiency and spectrum of a green random laser generated by frequency doubling of random fiber lasers.

Frequency doubling of random fiber lasers could provide an effective way to realize visible random lasing with the spectrum filled with random frequencies. In this paper, we make a comprehensive study on the efficiency and spectral manipulation of a green random laser generated by frequency doubling of an ytterbium-doped random fiber laser (YRFL). To tailor the efficiency of green random lasing generation, the ytterbium-doped random fiber lasing is filtered at different spectral positions, and then amplified to watt-level to serve as the fundamental laser source for frequency doubling in a periodically poled lithium niobate (PPLN) crystal. We found that by selecting different spectral components of ytterbium-doped random fiber lasing, the temporal intensity fluctuations of the filtered radiations vary dramatically, which plays an important role in enhancing the efficiency of frequency doubling. By fixing the filtering radiation wavelength at 1064.5 nm and tuning the central wavelength of YRFL, we experimentally demonstrate that, compared to the filtered radiation in the center of the spectrum, the efficiency of frequency doubling can be nearly doubled by utilizing the filtered ytterbium-doped random fiber lasing in the wings of the spectrum. As a result, the conversion efficiency of the generated green random laser at 532.25 nm can be more than 11% when the input power of the polarized 1064.5 nm fundamental light is 2.85W. For spectral manipulation, we realize a spectral tunable green random laser in the range of 529.9 nm to 537.3 nm with >100 mW output power for the first time by tuning the wavelength of YRFL and the temperature of PPLN simultaneously. The system can be naturally modified to simultaneously realize the efficiency enhancement and wavelength tuning, thus providing a new route to generate high efficiency and tunable visible random laser via frequency doubling that are potentially useful for imaging, sensing and visible light communication applications.

Diode End-Pumped 1.37 W Er:YSGG Continuous-Wave Laser Around 2.8-μm

We demonstrate the laser performance of a LD end-pumped Er:YSGG crystals with different doping concentrations comparatively. The experimental results show that 30 at. % Er:YSGG crystal with dimensions of 2 mm ×2 mm ×8 mm has the best laser output. In continuous-wave (CW) mode and pulse mode, the maximum output powers of 1.37 and 1.20 W are achieved, corresponding to slope efficiencies of 23.62% and 22.91%, respectively. To the best of our knowledge, compared with other Er <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped garnet laser crystals, we obtained a larger power and higher efficiency CW laser simultaneously for LD end-pumped Er:YSGG crystal. The beam quality factor M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in x and y directions are determined to be 1.64/1.65, suggesting the Er:YSGG laser possesses a higher beam quality. All these results indicate that Er:YSGG is a promising mid-infrared gain medium for high efficiency and high power laser operation.

190 °C High-Temperature Operation of 905-nm VCSELs With High Performance

Greater than 190 °C continuous wave (CW) lasing is achieved from 905 nm high-efficiency vertical cavity surface-emitting lasers (VCSELs). The maximum power conversion efficiency (PCE) of 46.3% for 4 μm VCSELs was demonstrated under the ambient temperature of 30 °C. The maximum PCE decreases only 10% of its value from 30 °C to 90 °C, showing stable high-temperature characteristics. The thermal resistances and active region temperatures of the device versus ambient temperature are determined experimentally. Besides, size-dependent thermal characteristics are also analyzed by characterizing the spectral and spatial properties of devices with various apertures. It is found that the higher the ambient temperature is, the less the number of high-order modes is, and single fundamental mode operation can be realized in 4 μm VCSELs even at a relatively high temperature of 190 °C. The design and characterization of these high-temperature VCSEL devices might present the basis for future laser radar application.

Quantitative evaluation and regulation of cold-ion system intrinsic micromotion by numerical simulation

The intrinsic micromotion of radio-frequency (RF) trapped three-dimensional (3D) cold ion systems plays an important role in the trapping, cooling, and manipulation of ions, and exhibits significantly different characteristics, compared to those of single-ion or chain-ion systems. In this study, the kinetic mechanism of the intrinsic micromotion of a 3D ion system is systematically studied, the 3D correlative coupling features between the intrinsic micromotion and secular motion are quantitatively assessed, and the transient evolution characteristics of the intrinsic micromotion are identified. In addition, the performances and application ranges of the two regulation methods, iso-q (stability trapping parameter) and iso-frequency, in inhibiting the intrinsic micromotion of 3D-ion crystals are compared, and a method for inhibiting intrinsic micromotion, while maintaining the spatial configuration of the 3D ion system is presented. The obtained results provide a basis for resolving the physical problems of 3D ion systems, such as long-term trapping without ion loss under a low heating rate, precision coherent manipulation, motion-effect inhibition, high-efficiency laser cooling, and sympathetic cooling. Furthermore, they facilitate the control of cold chemical reactions, coherence delay of the quantum states, and spectrum measurements approaching the theoretical precision limit of 3D ion systems.

Hundred-watt-level phosphosilicate Raman fiber laser with less than 1% quantum defect.

Quantum defect (QD)-induced high thermal load in high-power fiber lasers can largely affect the conversion efficiency, pose a threat to the system security, and even prohibit the further power scaling. In this Letter, we investigate evolutions and influences of the reflectivity of the output coupler, the length of phosphosilicate fiber, and the pump bandwidth, and demonstrate a hundred-watt-level low-QD Raman fiber laser (RFL). The RFL enabled by the boson peak of phosphosilicate fiber achieves a maximum power of 100.9 W with a reduced QD down to 0.97%; the corresponding conversion efficiency reaches 69.8%. This Letter may offer not only an alternative scheme for a high-power, high-efficiency fiber laser, but also great potential on the suppression of thermal-induced effects such as thermal mode instability and the thermal lens effect.

High-efficiency broadband tunable green laser operation of direct diode-pumped holmium-doped fiber

Green laser sources have become increasingly important for the application in scientific research and industry. Although several laser approaches have been investigated, the development of green lasers with the necessary efficiency and spectral characteristics required for practical deployment continues to attract immense interest. In this study, the efficient green laser operation of a Ho3+-doped fluoride fiber directly pumped by a commercial blue laser diode (LD) is experimentally investigated at various active fiber lengths. In the free-running laser, the slope efficiency was optimized up to 59.3% with 543.9 nm lasing, with respect to the launched pump power, using a 20-cm long active fiber. This is the maximum slope efficiency reported to date for a green fiber laser. A maximum output power of 376 mW at 543.5 nm was achieved by using a 17-cm long active fiber pumped at a maximum available launched pump power of 996 mW. Moreover, broadband tuning operation was demonstrated by employing a range of active fiber lengths, together with an intracavity bandpass filter. The operating wavelength was tunable from 536.3 nm to 549.3 nm. A maximum tuning power achieved was 118 mW at 543.4 nm for a 17-cm long active fiber. Moderate Ho3+-doped fiber length is shown to be effective in producing a high performance of a green fiber laser. The short-length of the active fiber considerably extends the green short wavelength operation due to limited reabsorption of the signal below 540 nm.

High-efficiency picosecond mode-locked laser using a thulium-doped nanoengineered yttrium-alumina-silica fiber as the gain medium.

We report the theoretical and experimental investigation of a self-starting mode-locked fiber laser with a nanoengineered Tm3+-doped yttrium-alumina-silica (YAS) fiber as the gain medium. The YAS fiber exhibits a higher capability of Tm3+ cluster elimination than commercial silica fibers. The Tm3+ fluorescence properties and YAS dispersion are well characterized. As a result, an efficient picosecond mode-locked fiber laser is demonstrated with a slope efficiency of 14.14% and maximum pulse energy of 1.27 nJ. To the best of our knowledge, this is the first mode-locked fiber laser based on a Tm3+-doped YAS fiber. The experimental observation is also supported by the numerical analysis.

Structure, first-principles calculations and yellow spectral properties of Dy3+: CaLaGa3O7 single crystal

High optical quality Dy3+-doped CaLaGa3O7 (abbreviated as Dy: CLGO below) crystal was grown successfully by the Czochralski technique along the (0 0 1) orientation. The lattice parameters of the as-grown crystal were obtained by Rietveld refinement to its XRD pattern. The electronic structures including band structure and density of state (DOS) were calculated by using first-principles calculations based on density functional theory (DFT). The spectroscopic characteristics of Dy: CLGO are investigated, with special attention to the yellow emission that could be pumped directly by the rapidly developed blue GaN LD. Based on the Judd-Ofelt (J-O) theory, the intensity parameters from the measured line strengths were determined. The J-O parameters were used to predict radiative transition probabilities, radiative lifetime and branching ratios for various excited levels of the Dy: CLGO crystal. The absorption cross-sections of Dy: CLGO at 453 nm are calculated to be 0.14 × 10−20 cm2 and 0.11 × 10−20 cm2 for π- and σ-polarizations, respectively. Meanwhile, Dy: CLGO exhibits strong yellow emission at 574 nm corresponding to the transition 4F9/2 → 6H13/2 with stimulated emission cross-sections of 3.88 × 10−21 cm2 and 3.42 × 10−21 cm2 for π- and σ-polarizations, respectively. The relatively long fluorescence lifetime (565 μs) indicates a high laser efficiency of the crystal. All results suggest that Dy: CLGO crystal could be a promising candidate for yellow laser at 574 nm pumped by blue GaN LD.

Narrow-linewidth high-efficiency single-frequency ytterbium-doped fiber laser with highly linear polarization at 1064 nm.

We present a linearly polarized single-longitudinal-mode (SLM) ytterbium-doped fiber laser with a polarization extinction ratio (PER) of over 35 dB and a narrow linewidth of less than 4.5 kHz. The very high PER is obtained by utilizing the polarization evolution effect at the optical fiber and the high-performance polarizing beam splitter. The SLM is achieved by using a segment of polarization-maintaining ytterbium-doped fiber as a narrowband filter. In addition, a high optical signal-to-noise ratio of 50 dB and a good slope efficiency of 60.5% are achieved. Using an ytterbium-doped fiber amplifier, a linearly polarized SLM laser system with a high power of over 2.5 W is demonstrated at 1064 nm.

Real-time monitoring and control for high-efficiency autonomous laser fabrication of silicon nanoparticle colloids

Nanotechnology is a significant research tool for biological and medical research with major advancements achieved from nanoparticle (Np) applications in biosensing and biotherapeutics. For laser ablation synthesis in solution (LASiS) to be chosen by researchers for Np colloid production, the process must effectively compete with chemical synthesis in terms of produced colloid quality and productivity while taking advantage of LASiS benefits in terms of its ‘green-synthesis’ and single-step functionalisation abilities. In this work, a newly developed integrated LASiS Np manufacturing system is presented including a Np flow reactor design, an at-line Np size monitoring via 180° dynamic light scattering, and a UV-Vis spectroscopy system used to estimate colloid concentration and stability. The experimental outcomes are discussed in terms of Np productivity and quality via these at-line measurements from the UV-Vis and DLS systems. The developed instrument was validated via off-line SiNps DLS, UV-Vis and morphology tests via TEM. Ultra-high quality and nanoparticle fabrication rate efficiency was achieved and is reported here.

5.1 kW Tandem-Pumped Fiber Amplifier Seeded by Random Fiber Laser With High Suppression of Stimulated Raman Scattering

In this work, high-power tandem-pumped random fiber lasers are investigated in detail. A 6.5 W random fiber laser seed centered at 1070 nm with a half-open cavity structure was built. Boosted by two amplifier stages, the random fiber laser achieved a power of several kilowatts. Stimulated Raman scattering (SRS) mitigation is challenging in tandem-pumped fiber lasers. To suppress SRS, several methods were applied, including avoiding external feedback in the oscillator stage, incorporating a high core/cladding diameter ratio gain fiber, and using a band pass filter (BPF) to mitigate Raman noise. The latter proved to be the most effective method; therefore, SRS mitigation without and with a BPF was investigated at 3.5 kW, leading to suppression ratios rising from 14 to 30 dB. By increasing the pump power continuously to 5.6 kW, we realized a record output power of 5.1 kW, corresponding to an SRS suppression ratio of 27 dB. Owing to the high-brightness 1018 nm fiber lasers serving as the pump sources and the high gain coefficient in the second amplifier stage, the entire system demonstrated high efficiency and stability. At the maximum power level, the total optical-to-optical efficiency reached 89.0%. This work offers an economic and practical technique for realizing high-power and high-efficiency random fiber lasers with effective SRS mitigation, while the experimental results suggest the potential for further power scaling.

LD-pumped 2.8 μm Er:Lu2O3 ceramic laser with 6.7 W output power and >30% slope efficiency

We present a high-power, high-efficiency, laser-diode-pumped 2.8 μm Er:Lu2O3 ceramic laser generating record power at room temperature. Careful thermal management and pump-radius enlargement resulted in a continuous-wave output power of 6.7 W at 2845 nm, with a 30.2% slope efficiency. To our knowledge, this is the highest output power and slope efficiency ever achieved from a laser-diode-pumped 3 μm Er-doped ceramic laser. These results confirm the possibility of generating high-output-power, high-efficiency laser using transparent ceramics.

Power threshold reduction and laser efficiency improvement of Brillouin fiber laser based on an As[formula omitted]S[formula omitted] Chalcogenide fiber via a mode field adaptor

A Brillouin fiber laser with low power threshold and high laser efficiency based on a 4.2-m-long As2S3 chalcogenide step-index fiber is presented in this work. Due to the free-space system between the As2S3 and single mode fiber (SMF), a high coupling efficiency is required to reduce the ring cavity loss and laser threshold, and hence improve the laser conversion efficiency. Compared with the lensed fiber and ultrahigh numerical aperture (UHNA) fiber which are commonly used as butt-coupling devices, the mode field adaptor (MFA) employed in this work can better match the mode field diameter and numerical aperture of the As2S3 and SMF, exhibiting a total coupling loss of only 1 dB. A low Brillouin laser threshold of 14 mW is achieved benefiting from the high cavity feedback of 16%. A Stokes power of ∼50 mW is generated for an injected pump power of 120 mW, showing a high laser efficiency of 42%. Furthermore, the Brillouin laser with the MFA butt-coupling exhibits lower relative intensity noise and phase noise and hence narrower laser linewidth than that with the lensed fiber and UHNA fiber butt-coupling. These results suggest the significance of the MFA which can reduce the cavity loss for a Brillouin laser with good performance based on As2S3 chalcogenide fiber.

Direct Tissue Mass Spectrometry Imaging by Atmospheric Pressure UV-Laser Desorption Plasma Postionization.

Matrix-assisted laser desorption ionization (MALDI) operated at atmospheric pressure has been shown to be a promising technique for mass spectrometry imaging of biological tissues at high spatial resolution. Recent studies have shown several orders of magnitude improvement in sensitivity afforded by coupling with a low-temperature plasma (LTP) for postionization. In this work we report the first results from "matrix-free" imaging using our atmospheric pressure (AP) transmission mode (TM) (MA)LDI source with LTP postionization. Direct MSI analysis of murine testis with no sample preparation after tissue sectioning enabled imaging of a range of lipid classes at pixel sizes of 25 μm. We compared results from the matrix-free methods with MALDI experiments in which the matrix was applied on top, underneath, or layered as a sandwich. The sandwich preparation was found to lead to ion yields approximately 2- or 3-fold higher than the other methods, indicating that the addition of a light absorbing matrix remains beneficial. Nonetheless, LDI methods confer a range of advantages, and the sensitivity improvements provided by postionization strategies are a promising step toward high-efficiency laser sampling under ambient conditions.

Development of High Performance C-Rich a-SiC Semiconductors with Narrow-Optical Gap By Control of Its Phase Structure

1. Introduction For the expansion of application fields (ex. tailor-made photocatalysts and high-efficiency laser) of semiconductor, novel semiconductor materials with variable optical gaps in the range from 1.2 to 3.0 eV is necessary to be developed. The promising candidate of these semiconductor is carbon-rich amorphous silicon-carbon alloy (C-rich a-SiC).[1] The optical gaps (Eog) of C-rich a-SiC can be changed from 1.2 to 2.7 eV by changing the Si/C ratio. Hetero-junction solar cell comprising N-doped C-rich a-SiC with Eog = 2.7 eV and p-type Si have been reported to show the function of photon to electron conversion.[2] However, solar cells comprising N-doped C-rich a-SiC with Eog from 1.2 to 1.7 eV showed extremely lower conversion efficiencies. Therefore, all of these C-rich a-SiC with Eog from 1.2 to 2.7 eV may not be applied to photoelectronic devices. The objective of this study is to realize C-rich a-SiC with lower Eog (frim 1.2 to 1.7 eV) that have higher semiconductor property and are able to be applied to photoelectronic devices. a-SiC has a multiphase structure in which amorphous Si-C network (Si:C = x:1-x), sp2-hybridized carbon cluster (sp 2 clusters), and silicon-like clusters (Si-cluster) coexist. It has been reported that excess sp2 cluster worked as a recombination center of photoexcited carries. It results in the degradation of efficiencies of photon to electron conversion. In order to realize C-rich a-SiC with lower Eog and higher photon to electron conversion efficiency, the synthesis method that can enhance of ratio of C/Si in amorphous Si-C network and suppress the formation of sp 2 clusters in C-rich a-SiC is necessary to be developed. In this study, CVD synthesis using high-frequency and lower power r. f. plasma was tried to be adopted to induce two types of structural change at C-rich a-SiC. High-frequency and lower power r. f. plasma can avoid the formation of sp 2 clusters in C-rich a-SiC. It results in the semiconductor materials with lower Eog and higher photon to electron conversion efficiency.2. Experimental Nitrogen-doped C-rich a-SiC thin films were synthesized by radio frequency plasma enhanced chemical vapor deposition system (RF-PeCVD) (13.56 MHz, SAMCO Co., Ltd. Model BPD-1) using tetramethylsilane, 1,1,3,3-tetrametyldisilazane and n-hexanes as source materials. C-rich a-SiC thin films were deposited on glass plate and boron-doped silicon (100) substrate (resistivity of 2 W cm) after an in-situ sputter cleaning with argon ions. Substrate temperature was kept at 160 degree C during CVD deposition. The frequency of r.f. power supply was set at 60 MHz and r.f power were changed from 5 to 26 W. The deposition time was 80 minutes. Transmission spectra of N-doped C-rich a-SiC deposited on glass substrates were examined by UV-Vis spectrophotometer (JASCO Co., Ltd. V-670). The performance of heterojunction solar cells was investigated by current-voltage (I-V) measurement (KEYSIGHT, B2901A) with simulated AM 1.5 sunlight (ASAHI SPECTRA, HAL-320). 3. Results and Discussion Eog estimated from transmission spectra (Fig. 1) of resulting N-doped C-rich a-SiC were found to be in the range from 1.40 to 2.96 eV, as shown in Table 1. Eog was able to be controlled to lower value (1.4 eV) thorough the change of the S/C ratios in C-rich a-SiC (by changing the volume ratio of n-hexane in source materials). All hetero-junction solar cells comprising N-doped C-rich a-SiC with various Eog and p-type Si crystal were confirmed to show the function of photon-to electron conversion (Table 1). The improvement of function of photon to electron conversion at C-rich a-SiC with lower Eog (ca. 1.4 eV) might be caused by the suppression of the recombination of photo-exited electrons and holes. In Figure 1, the absorption peak of sp 2 clusters was observed at 1.1 eV and was clearly separated from the absorption peak of amorphous Si-C network (observed at 2.6 eV). The intensity decrease and peak shift to lower energy side of the absorption of sp 2 clusters in Fig. 1 indicates the decrease of the amount of sp 2 clusters and the enlargement of size of sp 2 clusters. These structural change might cause the suppression of recombination of photo-carriers. The relation between Eog and open circuit voltage of solar cell was consistent with estimated value from electronic structure of C-rich a-SiC. It was summarized that the development of C-rich a-SiC semiconductors with lower Eog (in the range from 1.4 to 1.7 eV) that are able to be applied to photo-electronic devices was successfully achieved. 4.

Optical design and tolerance of a high efficiency laser polarization grating-polarization conversion system based and diffraction limited heads up display projector

In this paper, a compact and diffraction limited heads up display (HUD) image source is presented. The great benefit of this design is its diffraction limited optic, compacted structure, economic considerations, simplicity in manufacturing and high efficiency image quality. The innovation of this design is the use of a polarization grating-polarization conversion system (PG-PCS). This module transforms the unpolarized Gaussian beam to a linearly polarized beam and it simultaneously homogenizes the spatial intensity profile. With this module, it is possible to increase the efficiency of illumination and to utilize the ordinary micro LCD instead of using a digital micro mirror device (DMD) and liquid crystal on silicon (LCOS) micro displays. The diameter of the image plane is 76.2 mm (in accordance with conventional types). Our design yielded uniform illuminated image and its high efficiency facilitates display readability in see-through HUDs operating in high ambient light as well as low ambient light.