Vertical Cavity Surface Emitting Laser (VCSEL) is a type of semiconductor laser in which the laser emission direction is perpendicular to the P-N junction plane and the resonant cavity surface is parallel to the P-N junction plane, which is a type of surface emitting laser. The light of an EEL edge-emitting laser is emitted horizontally from the edge of the chip. Compared with EELs, VCSELs are more cost-effective and responsive, and are therefore replacing conventional edge-emitting lasers in an increasing number of applications.
Figure:Working principle of different light-emitting devices
With the development of optoelectronics and information technology, especially after equipment upgrading and process improvement, VCSELs have made great progress in both performance and application. Due to its advantages of low threshold current, stable working wavelength, good beam quality, easy one-dimensional and two-dimensional integration, VCSELs have been widely used in the fields of optical communication, laser display, optical storage, consumer electronics and so on.
Figure:Wide range of VCSEL sensing applications
Vertical Cavity Surface Emitting Lasers VCSELs have complex semiconductor structures, but their packaging structures are generally simpler. Unlike edge-emitting laser diodes, which need to be dissected into Bar strips to test for goodness, VCSELs can be tested and screened prior to packaging, greatly reducing the cost of product risk.There are three testing procedures in the VCSEL production process, all of which require a pulsed current source to test the device. A fast, flexible and highly accurate test program is essential to reduce the cost of testing.
Characterization of common VCSEL test parameters
VCSEL devices are widely used in 3D face recognition and distance sensing. When VCSEL arrays are used in TOF modules, especially in dTOF systems such as LIDAR, the peak power, operating current, operating voltage, conversion efficiency, near- and far-field optical characteristics and other parameters of VCSELs in the case of narrow pulses are very important for chip vendors, packaging service providers, module integrators and so on.
VCSEL and VCSEL arrays, including a variety of laser diode standard testing of the key electrical performance parameters, common such as laser diode forward voltage drop (VF), KinK point test / linearity test (dL / dI), threshold current (lth), output optical power (Po) to slope efficiency (Es), and so on.
The LIV test is a fast and simple method of determining the key performance parameters of a VCSEL by combining two measurement curves in a single graph.The L/I curve shows the dependence of the laser's light intensity on the operating current and is used to determine the operating point and threshold current.The V/I curve shows the voltage applied to the laser as a function of the operating current.The V/I curve shows the voltage applied to the laser as a function of the operating current. The LIV (Light Intensity - Current - Voltage) test makes it possible to evaluate the characteristics of most of the electrical parameters of the VCSEL and the optimal output optical power.
The narrower the laser pulse width of the radar output, the higher the ranging accuracy; the higher the peak optical power, generally need to hundreds of watts, the longer the test distance. Therefore, it is very critical to study the high peak optical power VCSEL chip with high injection current. High-power lasers use DC or broad pulse charging serious heat, laser effects by the temperature is very large, DC or broad pulse test results do not reflect the device characteristics. Therefore, in order to measure the performance of VCSEL devices in real operating scenarios, it is necessary to have test equipment with microsecond or even nanosecond driving and testing capabilities, which cannot be met by the current traditional DC or broad pulse test instrumentation.
Typical Solution for PL Series Narrow Pulse LIV Test System
In order to meet the demand of VCSEL industry chain for narrow pulse LIV test, Purcells Instruments and the head enterprises in multiple application fields have carried out in-depth discussions, combined with the industrial demand and their own technical precipitation, launched the PL narrow pulse LIV test system, the product has a narrow output current pulse (ns level), large output pulse current (30A), support for the pulse peak power detection, support for the laser voltage measurement, ultra-fast rise speed and other functions. The product is characterized by narrow output current (ns level), large output current (30A), support for peak power detection, laser voltage measurement, and ultra-fast rise speed.
Fig.:Block diagram of PL series narrow pulse LIV test system and test system
PL series narrow pulse LIV test system composition as shown in the figure above: PL series pulse source, test fixture, integrating sphere, fiber optic, spectrometer, etc., spectrometer users can choose to purchase another according to their own needs.
System Advantages
Multi-meter functions in one: fast pulse generator + programmable current source + peak sampling optical power meter + pulse voltmeter
1、PL series LIV test system has the characteristics of good synchronization performance, fast test speed and complete solution.
2, through the 15MS / s digitalization function, to achieve the pulse generator 0.1% basic measurement accuracy.
3, ultra-narrow to ns-level pulse, duty cycle can be as low as 0.01%.
4、Multiple precision photocurrent test ranges.
5, the upper computer LIV algorithm, support for automatic calculation of various parameters, simplify the application.
Purcell PL series narrow pulse system LIV test scan can perform forward voltage (VF) test, threshold current (lth) test, light intensity (L) test, and optical characteristic parameter test.
Rich product line, multi-channel aging power supply to meet the VCSEL laser aging test needs
Since the introduction of semiconductor lasers, due to their material and structural characteristics, they have been facing the problem of service life degradation, and it is necessary to carry out aging tests on the laser chips to screen out components with potential quality problems and to satisfy their million-hour operating time.
For the demand of aging power supply for VCSEL test system, Purcell's rich product line can also cope with it. Multi-channel aging power supply, up to 40CH, each channel can be independently controlled, synchronous testing, independent output, flexible configuration, to help VCSEL aging test to achieve accurate and efficient.
Please feel free to contact us for information on the full range of digital source meters (SMUs) and application solutions from Purcell.
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