What is a photomixer and how does it generate continuous wave terahertz radiation?
Photomixing Technology for Tunable CW Terahertz Sources
Photomixing bridges the optical and electronic worlds by using ultrafast photodetection to convert a tunable optical frequency difference into coherent terahertz radiation.
| Parameter | Option A | Option B | Option C |
|---|---|---|---|
| Performance | High | Medium | Low |
| Cost | High | Low | Medium |
| Complexity | High | Low | Medium |
| Bandwidth | Narrow | Wide | Moderate |
| Typical Use | Lab/military | Consumer | Industrial |
Technical Considerations
Two laser beams at frequencies f1 and f2 are combined and focused onto a small-area photoconductor. The optical interference creates sinusoidal intensity modulation at f_THz = |f1 - f2|. A planar antenna radiates this current as terahertz radiation.
Performance Analysis
A complete system consists of two tunable laser sources, an optical combiner, polarization control, fiber delivery to the photomixer chip, and a silicon hyper-hemispherical lens. Coherent detection uses a second photomixer as the receiver.
Design Guidelines
When evaluating a photomixer and how does it generate continuous wave terahertz radiation?, engineers must account for the specific requirements of their target application. The optimal choice depends on the frequency range, power level, environmental conditions, and cost constraints of the overall system design.
Implementation Notes
When evaluating a photomixer and how does it generate continuous wave terahertz radiation?, engineers must account for the specific requirements of their target application. The optimal choice depends on the frequency range, power level, environmental conditions, and cost constraints of the overall system design.
- Performance verification: confirm specifications against the application requirements before finalizing the design
- Environmental factors: temperature range, humidity, and vibration affect long-term reliability and parameter drift
- Cost vs. performance: evaluate whether the application demands premium components or standard commercial grades
- Interface compatibility: verify impedance, connector type, and mechanical form factor match the system architecture
- Margin allocation: include sufficient design margin to account for manufacturing tolerances and aging effects
Practical Applications
When evaluating a photomixer and how does it generate continuous wave terahertz radiation?, engineers must account for the specific requirements of their target application. The optimal choice depends on the frequency range, power level, environmental conditions, and cost constraints of the overall system design.
Frequently Asked Questions
How much output power can I get from a photomixer at 1 THz?
A typical LT-GaAs photomixer produces 0.1-1 microwatt at 1 THz with 20-30 mW of total optical pump power. UTC-PDs produce higher power (10-100 microwatts at 300 GHz).
What lasers are used to drive a photomixer?
For LT-GaAs photomixers, tunable external-cavity diode lasers or Ti:Sapphire lasers at 780-850 nm. For InGaAs photomixers, fiber-coupled DFB lasers at 1550 nm.
Can photomixers be used for terahertz spectroscopy?
Yes. CW photomixer spectroscopy achieves frequency resolution below 1 MHz, far superior to pulsed THz-TDS systems (typical resolution 1-10 GHz).