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Qiu, Yueming

Publications and source records attributed to Qiu, Yueming.

16 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

What drives embodied carbon policy? A global perspective on adoption

Abstract Embodied carbon refers to the greenhouse gas emission associated with the lifecycle of buildings. Embodied carbon policies are critical for addressing the environmental impact of construction materials and advancing climate goals. Despite their importance, the adoption of embodied carbon policies has been limited globally, influenced by economic, environmental, institutional, and trade factors. This study employs structural equation modeling to analyze 37 countries, testing ten hypotheses across four categorical factors. The base model reveals the significant influence of environmental vulnerability and institutional frameworks on policy adoption, while robustness models confirm the critical role of trade dependencies and economic competitiveness in shaping national embodied carbon strategies. Findings underscore that countries with high climate vulnerability and strong institutional support are more likely to adopt embodied carbon policies. Conversely, trade-reliant nations face challenges balancing competitiveness and sustainability. Policy implications suggest the need for international collaboration to align trade policies with carbon reduction goals, targeted support for vulnerable nations, and the integration of embodied carbon considerations into existing climate frameworks. These results offer a roadmap for policymakers to design more effective and equitable embodied carbon policies, fostering global progress toward sustainable construction and decarbonization.

Hu, Ming (ORCID:0000000325831161)↗
NASA NTRS2012

Reliable Optical Pump Architecture for Highly Coherent Lasers Used in Space Metrology Applications

The design and initial demonstration of a laser pump module (LPM) incorporating single-mode, grating-stabilized 808-nm diode lasers and a low-loss, high-port-count optical combiner are completed. The purpose of the developed LPM is to reliably pump an Nd:YAG crystal in the laser head (LH), which serves as the optical metrology source for SIMLite mission. Using the narrow-linewidth, single-mode laser diodes enables placement of the pump power near Nd adsorption peak, which enhances pumping efficiency. Grating stabilization allows for stable pump spectra as diode operating temperature and bias current change. The low-loss, high-port-count optical combiner enables efficient combining of tens of pumps. Overall, the module supports 5+ years of continuous operation at 2 W of pump power with reliability approaching 100 percent. The LPM consists of a laser diode farm (LDF) and a pump beam combiner (PBC). An array of 807- to 808-nm fiber-pigtailed laser diodes makes up the LDF. A Bragg grating in each 5- m core single-mode (SM) fiber pigtail acts to stabilize the lasing spectra over a range of diode operating conditions. These commercially available single-mode laser diodes can deliver up to 150 mW of optical power. The outputs from the multiple pumps in the LDF are routed to the PBC, which is a 37-input by 1-output all-fiber device. The input ports consist of 5- m core SM fiber, while the output port consists of 105- m core, 0.15 NA (numerical aperture) multi-mode (MM) fiber. The combiner is fabricated by fusing the 37 input fibers while simultaneously tapering the fused region. At the completion of this process, the MM fiber is spliced to the end of the adiabatic taper, and, for protection, the combiner is sheathed by a capillary tube. A compact and robust metal housing was designed and fabricated to protect the PBC during space deployment.

Erlig, Herman↗
NASA NTRS2010

Low Power Consumption Lasers for Next Generation Miniature Optical Spectrometers for Major Constituent and Trace Gas Analysis

The air quality of any manned spacecraft needs to be continuously monitored in order to safeguard the health of the crew. Air quality monitoring grows in importance as mission duration increases. Due to the small size, low power draw, and performance reliability, semiconductor laser-based instruments are viable candidates for this purpose. The minimum instrument size requires lasers with emission wavelength coinciding with the absorption of the fundamental frequency of the target gases which are mostly in the 3.0-5.0 micrometers wavelength range. In this paper we report on our progress developing high wall plug efficiency type-I quantum-well GaSb-based diode lasers operating at room temperatures in the spectral region near 3.0-3.5 micrometers and quantum cascade (QC) lasers in the 4.0-5.0 micrometers range. These lasers will enable the development of miniature, low-power laser spectrometers for environmental monitoring of the spacecraft.

semiconductor lasers↗
NASA NTRS2008

Reliability of Semiconductor Laser Packaging in Space Applications

A typical set up used to perform lifetime tests of packaged, fiber pigtailed semiconductor lasers is described, as well as tests performed on a set of four pump lasers. It was found that two lasers failed after 3200, and 6100 hours under device specified bias conditions at elevated temperatures. Failure analysis of the lasers indicates imperfections and carbon contamination of the laser metallization, possibly from improperly cleaned photo resist. SEM imaging of the front facet of one of the lasers, although of poor quality due to the optical fiber charging effects, shows evidence of catastrophic damage at the facet. More stringent manufacturing controls with 100% visual inspection of laser chips are needed to prevent imperfect lasers from proceeding to packaging and ending up in space applications, where failure can result in the loss of a space flight mission.

Gontijo, Ivair↗
NASA NTRS2007

High-Reliability Pump Module for Non-Planar Ring Oscillator Laser

We propose and have demonstrated a prototype high-reliability pump module for pumping a Non-Planar Ring Oscillator (NPRO) laser suitable for space missions. The pump module consists of multiple fiber-coupled single-mode laser diodes and a fiber array micro-lens array based fiber combiner. The reported Single-Mode laser diode combiner laser pump module (LPM) provides a higher normalized brightness at the combined beam than multimode laser diode based LPMs. A higher brightness from the pump source is essential for efficient NPRO laser pumping and leads to higher reliability because higher efficiency requires a lower operating power for the laser diodes, which in turn increases the reliability and lifetime of the laser diodes. Single-mode laser diodes with Fiber Bragg Grating (FBG) stabilized wavelength permit the pump module to be operated without a thermal electric cooler (TEC) and this further improves the overall reliability of the pump module. The single-mode laser diode LPM is scalable in terms of the number of pump diodes and is capable of combining hundreds of fiber-coupled laser diodes. In the proof-of-concept demonstration, an e-beam written diffractive micro lens array, a custom fiber array, commercial 808nm single mode laser diodes, and a custom NPRO laser head are used. The reliability of the proposed LPM is discussed.

micro lens array↗
NASA NTRS2007

Diffractive Combiner of Single-Mode Pump Laser-Diode Beams

An optical beam combiner now under development would make it possible to use the outputs of multiple single-mode laser diodes to pump a neodymium: yttrium aluminum garnet (Nd:YAG) nonplanar ring oscillator (NPRO) laser while ensuring that the laser operates at only a single desired frequency. Heretofore, an Nd:YAG NPRO like the present one has been pumped by a single multimode laser-diode beam delivered via an optical fiber. It would be desirable to use multiple pump laser diodes to increase reliability beyond that obtainable from a single pump laser diode. However, as explained below, simplistically coupling multiple multimode laser-diode beams through a fiber-optic combiner would entail a significant reduction in coupling efficiency, and lasing would occur at one or more other frequencies in addition to the single desired frequency. Figure 1 schematically illustrates the principle of operation of a laser-diode-pumped Nd:YAG NPRO. The laser beam path is confined in a Nd:YAG crystal by means of total internal reflections on the three back facets and a partial-reflection coating on the front facet. The wavelength of the pump beam - 808 nm - is the wavelength most strongly absorbed by the Nd:YAG crystal. The crystal can lase at a wavelength of either 1,064 nm or 1,319 nm - which one depending on the optical coating on the front facet. A thermal lens effect induced by the pump beam enables stable lasing in the lowest-order transverse electromagnetic mode (the TEM00 mode). The frequency of this laser is very stable because of the mechanical stability of the laser crystal and the unidirectional nature of the lasing. The unidirectionality is a result of the combined effects of (1) a Faraday rotation induced by an externally applied magnetic field and (2) polarization associated with non-normal incidence and reflection on the front facet.

Liu, Duncan↗
NASA NTRS2006

Quantum-Dot Laser for Wavelengths of 1.8 to 2.3 micron

The figure depicts a proposed semiconductor laser, based on In(As)Sb quantum dots on a (001) InP substrate, that would operate in the wavelength range between 1.8 and 2.3 m. InSb and InAsSb are the smallest-bandgap conventional III-V semiconductor materials, and the present proposal is an attempt to exploit the small bandgaps by using InSb and InAsSb nanostructures as midinfrared emitters. The most closely related prior III-V semiconductor lasers are based, variously, on strained InGaAs quantum wells and InAs quantum dots on InP substrates. The emission wavelengths of these prior devices are limited to about 2.1 m because of critical quantum-well thickness limitations for these lattice mismatched material systems. The major obstacle to realizing the proposed laser is the difficulty of fabricating InSb quantum dots in sufficient density on an InP substrate. This difficulty arises partly because of the weakness of the bond between In and Sb and partly because of the high temperature needed to crack metalorganic precursor compounds during the vapor-phase epitaxy used to grow quantum dots: The mobility of the weakly bound In at the high growth temperature is so high that In adatoms migrate easily on the growth surface, resulting in the formation of large InSb islands at a density, usually less than 5 x 10(exp 9) cm(exp -2), that is too low for laser operation. The mobility of the In adatoms could be reduced by introducing As atoms to the growth surface because the In-As bond is about 30 percent stronger than is the In-Sb bond. The fabrication of the proposed laser would include a recently demonstrated process that involves the use of alternative supplies of precursors to separate group-III and group-V species to establish local non-equilibrium process conditions, so that In(As)Sb quantum dots assemble themselves on a (001) InP substrate at a density as high as 4 x 10(exp 10) cm(exp -2). Room-temperature photoluminescence spectra of quantum dots formed by this process indicate that they emit at wavelengths from 1.7 to 2.3 microns.

Qiu, Yueming↗
NASA NTRS2006

Development of Efficient Mid-IR Interband Cascade Lasers for Chemical Sensing

Significant progress has been made: Above room temperature (up to 350K) pulsed operation has been demonstrated. CW operation temperature has been raised up to 237 K. DFB IC lasers have been applied for the detection of trace gases such as CH4, HCl, and H2CO. Devices have been operated continuously over several hundred hours without degradation. Main challenge remains for many potential applications of ICLs. CW operation at room temperature and above with significant output powers. There is still significant room for improvement: Laser design and material quality - many parameters have not been optimized. Device fabrication and thermal management (passivation, better mounting, etc.). Significantly higher output power can be achieved with laser arrays.

diode lasers↗
NASA NTRS2005

Mid-IR interband cascade lasers

Efficient mid-IR interband cascade (IC) lasers are developed based on 111-V semiconductor materials to cover wavelength range from 2.7 to 5.6 (mu)m. These IC lasers reuse injected electrons in cascade stages for photon generation with high quantum efficiency to achieve high output powers. Also, IC lasers have low threshold current density with very efficient use of applied voltage, resulting in reduced power consumptions. Single-mode distributed feedback lasers have been made, and integrated into aircraft and balloon instrument which made measurements of CH4 and HCI. In this work, the characteristics of IC lasers and their recent development are reviewed.

mid - infrared↗
NASA NTRS2005

Adding GaAs Monolayers to InAs Quantum-Dot Lasers on (001) InP

In a modification of the basic configuration of InAs quantum-dot semiconductor lasers on (001)lnP substrate, a thin layer (typically 1 to 2 monolayer thick) of GaAs is incorporated into the active region. This modification enhances laser performance: In particular, whereas it has been necessary to cool the unmodified devices to temperatures of about 80 K in order to obtain lasing at long wavelengths, the modified devices can lase at wavelengths of about 1.7 microns or more near room temperature. InAs quantum dots self-assemble, as a consequence of the lattice mismatch, during epitaxial deposition of InAs on ln0.53Ga0.47As/lnP. In the unmodified devices, the quantum dots as thus formed are typically nonuniform in size. Strainenergy relaxation in very large quantum dots can lead to poor laser performance, especially at wavelengths near 2 microns, for which large quantum dots are needed. In the modified devices, the thin layers of GaAs added to the active regions constitute potential-energy barriers that electrons can only penetrate by quantum tunneling and thus reduce the hot carrier effects. Also, the insertion of thin GaAs layer is shown to reduce the degree of nonuniformity of sizes of the quantum dots. In the fabrication of a batch of modified InAs quantum-dot lasers, the thin additional layer of GaAs is deposited as an interfacial layer in an InGaAs quantum well on (001) InP substrate. The device as described thus far is sandwiched between InGaAsPy waveguide layers, then further sandwiched between InP cladding layers, then further sandwiched between heavily Zn-doped (p-type) InGaAs contact layer.

Qiu, Yueming↗
NASA NTRS2004

Growing High-Quality InAs Quantum Dots for Infrared Lasers

An improved method of growing high-quality InAs quantum dots embedded in lattice-matched InGaAs quantum wells on InP substrates has been developed. InAs/InGaAs/InP quantum dot semiconductor lasers fabricated by this method are capable of operating at room temperature at wavelengths greater than or equal to 1.8 mm. Previously, InAs quantum dot lasers based on InP substrates have been reported only at low temperature of 77 K at a wavelength of 1.9 micrometers. In the present method, as in the prior method, one utilizes metalorganic vapor phase epitaxy to grow the aforementioned semiconductor structures. The development of the present method was prompted in part by the observation that when InAs quantum dots are deposited on an InGaAs layer, some of the InAs in the InGaAs layer becomes segregated from the layer and contributes to the formation of the InAs quantum dots. As a result, the quantum dots become highly nonuniform; some even exceed a critical thickness, beyond which they relax. In the present method, one covers the InGaAs layer with a thin layer of GaAs before depositing the InAs quantum dots. The purpose and effect of this thin GaAs layer is to suppress the segregation of InAs from the InGaAs layer, thereby enabling the InAs quantum dots to become nearly uniform (see figure). Devices fabricated by this method have shown near-room-temperature performance.

Qiu, Yueming↗
NASA NTRS2004

2 Micrometers InAsSb Quantum-dot Lasers

InAsSb quantum-dot lasers near 2 micrometers were demonstrated in cw operation at room temperature with a threshold current density of 733 A,/cm(sup 2), output power of 3 mW/facet and a differential quantum efficiency of 13%.

quantum dot↗
NASA NTRS2004

Semiconductor Lasers Containing Quantum Wells in Junctions

In a recent improvement upon In(x)Ga(1-x)As/InP semiconductor lasers of the bipolar cascade type, quantum wells are added to Esaki tunnel junctions, which are standard parts of such lasers. The energy depths and the geometric locations and thicknesses of the wells are tailored to exploit quantum tunneling such that, as described below, electrical resistances of junctions and concentrations of dopants can be reduced while laser performances can be improved. In(x)Ga(1-x)As/InP bipolar cascade lasers have been investigated as sources of near-infrared radiation (specifically, at wavelengths of about 980 and 1,550 nm) for photonic communication systems. The Esaki tunnel junctions in these lasers have been used to connect adjacent cascade stages and to enable transport of charge carriers between them. Typically, large concentrations of both n (electron-donor) and p (electron-acceptor) dopants have been necessary to impart low electrical resistances to Esaki tunnel junctions. Unfortunately, high doping contributes free-carrier absorption, thereby contributing to optical loss and thereby, further, degrading laser performance. In accordance with the present innovation, quantum wells are incorporated into the Esaki tunnel junctions so that the effective heights of barriers to quantum tunneling are reduced (see figure).

Yang, Rui Q.↗
NASA NTRS2004

Self-assembled InAsSb quantum dots on (001) InP substrates

Self-assembled InAsSb quantum dots (QD) on (001) InP substrates have been grown using metalorganic vapor phase epitaxy. The dot density and size are found to be strongly dependent on the presence of arsine. Direct deposition of InSb on InP and GaSb substrates formed large islands of InSb with low density of less than 53109/cm², however, InAsSb QDs of density as high as 4 X10¹º/cm² could be self-assembled by alternating group III and group V precursors, and high density almost pure InSb QDs were achieved on In0.53Ga0.47As/InP. The formation of high density InAsSb QDs is a result of a local nonequilibrium process and a reduction in mobility of In adatoms on the growth surface due to the presence of arsenic atoms, and in the case of high density almost pure InSb QDs on InGaAs/InP, the InAs interface layer is believed to be responsible. Photoluminescence shows that InSb QDs emit light at room temperature in the range of 1.7–2.2µm.

Uhl, David↗
NASA NTRS2001

Semiconductor Reference Oscillator Development for Coherent Detection Optical Remote Sensing Applications

The NASA Earth Science Enterprise Advanced Technology Initiatives Program is supporting a program for the development of semiconductor laser reference oscillators for application to coherent optical remote sensing from Earth orbit. Local oscillators provide the frequency reference required for active spaceborne optical remote sensing concepts that involve heterodyne (coherent) detection. Two recent examples of such schemes are Doppler wind lidar and tropospheric carbon dioxide measurement by laser absorption spectrometry, both of which are being proposed at a wavelength of 2.05 microns. Frequency-agile local oscillator technology is important to such applications because of the need to compensate for large platform-induced Doppler components that would otherwise interfere with data interpretation. Development of frequency-agile local oscillator approaches has heretofore utilized the same laser material as the transmitter laser (Tm,Ho:YLF in the case of the 2.05-micron wavelength mentioned above). However, a semiconductor laser-based frequency-agile local oscillator offers considerable scope for reduced mechanical complexity and improved frequency agility over equivalent crystal laser devices, while their potentially faster tuning capability suggest the potential for greater scanning versatility. The program we report on here is specifically tasked with the development of prototype novel architecture semiconductor lasers with the power, tunability, and spectral characteristics required for coherent Doppler lidar. The baseline approach for this work is the distributed feedback (DFB) laser, in which gratings are etched into the semiconductor waveguide structures along the entire length of the laser cavity. However, typical DFB lasers at the wavelength of interest have linewidths that exhibit unacceptable growth when driven at the high currents and powers that are required for the Doppler lidar application. Suppression of this behavior by means of corrugation pitch-modulation (using a detuned central section to prevent intensity peaking in the center of the cavity) is currently under investigation to achieve the required performance goals.

distributed feedback (DFB) laser↗