| 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 |
Table Comparison Chart : Various Lasers
| 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,N2 and 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 |
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