NITRIDE-BASED HETEROSTRUCTURES FOR UV LASERS

Introduction

III-nitride heterostructures enable UV lasers for sensing, medical,

security apps

Lasers needed in UVA (320-400nm), UVB (280-320nm), UVC

(<280nm) bands

AlGaN, InGaN, InAlGaN based quantum well structures being

explored

AlGaN MQW Lasers

Lasing demonstrated down to 241nm at room temperature

Threshold pumping power around 1200 kW/cm2

Gain around 120 cm-1 achieved in AlGaN/AlN MQWs

Effect of Delta Layer Insertion

Inserting thin delta layers of GaN or AlGaN in QWs

Creates high carrier confinement and strain

Enhances UV emission intensity and optical gain

6-7x gain improvement reported with delta layers

Optical Gain Optimization

Reducing QW width significantly boosts optical gain

Gain over 8000 cm-1 achieved in GaN/AlGaN with 40nm QW

High gain ~1700 cm-1 in 2nm thick AlGaN QW at 270nm

Conclusion

Nitride heterostructures offer promising performance for UV lasers

Delta layers and QW engineering enable gain enhancement

Further advances needed towards electrically injected UV lasers

Key Highlights

III-nitrides uniquely enable UV laser diodes

Intelligent heterostructure design is key for high gain

Thin delta layers dramatically improve carrier confinement

With optimized designs, high gain demonstrated down to 240nm

Essential progress towards on-chip UV sources for sensing

applications

PHOTONIC CRYSTAL BIOSENSOR FOR BLOOD ANALYSIS

Introduction

Blood analysis important for detecting hematological disorders

Diseases cause changes in blood composition and refractive index

Photonic crystal biosensors detect refractive index changes

Design Structure

GaN substrate with air holes in photonic crystal configuration

Line defect waveguide introduced in photonic crystal

Elliptical sensing nodes in defect with blood component as analyte

Simulation Results

Photonic bandgap from 1340-1570 nm

Resonance wavelength shifts from 1556 to 1528 nm for RI 1.33 to

1.45

Quality factor around 210

High sensitivity of 230 nm/RIU

Allows detection of small refractive index changes

Conclusion

Compact photonic crystal sensor designed for blood analysis

Resonance peak shift allows detection of variations in blood

composition

High sensitivity enables identifying minor refractive index changes

Can aid early diagnosis of hematological disorders

Key Highlights

Photonic crystals allow creating integrated optical biosensors

Refractive index changes of blood composition detected by

resonance shift

High Q-factor gives good confinement for sensitivity

Compact on-chip GaN photonic crystal sensor demonstrated

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