Difference Between Homojunction & Heterojunction Laser

S. No	Homojuction Laser	Heterojunction Laser
1.	Homojunction laser is made by a single crystalline material.	Heterojunction laser is made by different crystalline materials.
2.	Power output is low	Power output is high
3.	Pulsed output	Continuous output
4.	It has high threshold	Has low threshold current density
5.	Cost is less	Cost is more
6.	Life time is less	Life time is more
7.	Example: (i)GaAs (ii)InP	Example: (i)GaAs/ GaAlAs (ii)InP/ InAlP

Characteristics	Nd-YAG Laser	CO₂ Laser	Semiconductor laser (GaAs)	Semiconductor laser (GaAs/ GaAlAs )
Type	Doped insulator laser.	Molecular gas laser.	Homojunction semiconductor laser.	Heterojunction semiconductor laser.
Active medium	Yttrium Aluminium Garnet (Y₃Al₅O₁₂ )	Mixture of CO₂,N₂and helium (or) water vapour.	p-n junction diode.	p-n junction made from different layers.
Active center	Neodymium( Nd³⁺ )	CO₂	Recombination of electrons and holes.	Recombination of electrons and holes.
Pumping method	Optical Pumping	Electric discharge.	Direct pumping	Direct conversion method.
Optical resonator	Two mirrors,one of them is totally reflecting and the other is partially reflecting.	Metallic mirror of gold or silicon mirror coated with aluminium.	Junction of diodes – polished.	Polished junctions of diode.
Power output	2×10⁴ Watts	10kW	1 mW -10 mW	10 mW
Nature of output	Pulsed	Continuous (or) Pulsed.	Continuous Waveform or pulsed.	Continuous Waveform.
Wave Length	1.06 μm	9.6 – 10.6 μm	8400Å-8600Å	8000Å