Laser diodes and VCSELs as technology drivers
Laser diodes are becoming indispensable in a multitude of everyday and industrial applications, thereby expediting new applications and technologies. These include:
- Facial and gesture recognition in consumer electronics
- LiDAR (light detection and ranging) in the car
- Material processing with high-performance diode lasers
VCSELs are replacing EELs
Laser diodes can be technologically subdivided into EELs (edge-emitting laser) and VCSEL (vertical cavity surface-emitting laser). EELs are edge emitters and emit horizontally to the chip surface. They can be optically characterized only after reflecting surfaces have been attached to the chip edges.
In contrast VCSELs – analogous to LEDs – are surface emitters and emit vertically to the chip surface. The layer structure incorporates the mirror required for the laser cavity. This permits optical characterization of the VCSEL already on the wafer. The VCSEL production process is thus more economical than that of EEL, with the result that they are replacing conventional laser systems in an increasing number of applications.
The need for suitable measuring systems for efficient, high-precision optical characterization of these narrow-band light sources is increasing accordingly. As the temporal behavior of laser pulses for many applications is critical, the characterization of the pulse length down to a nanosecond is important.
When must laser diodes be measured?
Laser diodes are used in combination with a sensor system In many applications, e.g. facial recognition or LiDAR. An accuracte knowledge of the emitted wavelength and power of the laser is essential here for reconciliation with the respective sensor system.
The sorting of laser diodes in production on the basis of optical properties forms part of the in-process inspection system. To ensure the proper functioning of a component, it must be inspected for conformance to specifications within prescribed tolerance limits.
In order to avoid eye damage, laser diodes to be used in the presence of humans must satisfy laser safety requirements. These laser diodes – in particular pulse-operated laser diodes – must be accurately measured with regard to their energy and performance.
The challenge: Spectral measurement of laser diodes
Measuring systems for laser diodes must satisfy special requirements:
- High spectral resolution
- High throughput volumes in production
- Spectral measurement of pulsed laser diodes
Requirements for pulse measurements:
- Very short pulse lengths (≥ 1 ns) at extremely high currents (up to 15A)
- High sampling rates of several gigahertz
- The measurement of pulse trains calls for fast processing of large data volumes.
Solution: High-resolution spectroradiometers from Instrument Systems
The CAS 140CT-HR and CAS 120(B)-HR high-resolution array spectroradiometers from Instrument Systems are the flagships of our systems for VCSEL measurement. They enable excellent spectral resolution up to 0.12 nm, and due to short integration times they are ideal for use not only in the lab, but also for extremely high throughput volumes in production.
The spectrometers from Instrument Systems guarantee - without additional calibration of the complete VCSEL test system - a direct and traceable measurement of radiant flux.
All-in-one system PVT 110 for the measurement of nanosecond pulses
Instrument Systems developed the PVT 110 specifically for time-resolved measurement of nanosecond pulses. This system has an extremely broad range of applications with the use of different photodiodes for power measurement and characterization of fast pulses, together with fast measurement and analysis of all resulting data flows.
We look forward to your challenge – feel free to contact us!