What is a diode array detector? The basic structure, advantages and disadvantages, working principle, application, classification, operating procedures, and development history of diode array detectors

A diode array detector (DAD) is a commonly used optical detector for spectroscopic measurements in analytical chemistry, such as infrared spectroscopy, ultraviolet spectroscopy, and fluorescence spectroscopy. It is composed of an array of multiple diodes, each diode corresponding to a detection channel, which can simultaneously measure optical signals of multiple wavelengths and achieve multi-channel simultaneous detection.

1、 Basic structure:

A diode array detector is composed of an array of multiple diodes. Each diode can independently detect light signals of specific wavelengths. Typically, a diode array detector consists of eight or more diodes, each corresponding to a specific wavelength range. These diodes are typically installed in a sealed metal casing to protect them from external light and environmental interference.

2、 Advantages and disadvantages:

advantage:

1. High sensitivity: Multi channel simultaneous detection improves detection sensitivity.

2. Wide dynamic range: can handle samples with different concentration ranges.

3. High resolution: With high resolution, it can accurately measure wavelengths.

4. Real time detection: It can monitor sample changes in real time.

5. Multi channel detection: It can simultaneously measure optical signals of multiple wavelengths, improving detection efficiency.

Disadvantages:

1. High price: Compared to other commonly used optical detectors, diode array detectors are more expensive.

2. Channel limit: Because each channel requires one diode, the number of diodes limits the increase in channel count.

3、 Working principle:

The working principle of a diode array detector is based on the photoelectric effect. When light shines on a diode, the energy of photons is converted into the energy of electrons, thereby generating an electric current on the diode. This current signal is amplified and converted into a digital signal, which is then processed and analyzed by a computer. Different wavelengths of light can be detected and recorded through different diodes.

4、 Application:

Diode array detectors are widely used in spectroscopic measurements in analytical chemistry, such as infrared spectroscopy, ultraviolet spectroscopy, and fluorescence spectroscopy. It can be used to analyze the composition, concentration, mass, and reaction kinetics of substances.

5、 Category:

According to their different structures and working principles, they can be divided into the following categories:

1. PN junction diode array detector: an array composed of multiple PN junction diodes, each diode can work independently, with high sensitivity and low noise. Suitable for fields such as high-speed optical communication and fiber optic sensing.

2. Piezoelectric diode array detector: using piezoelectric effect to convert optical signals into charge signals. It has fast response, high sensitivity, and broadband characteristics, suitable for high-speed optical communication and fiber optic sensing fields.

3. Photodiode array detector: an array composed of multiple photodiodes, each of which can work independently. It has the characteristics of high-speed response, high sensitivity, and low noise, and is suitable for high-speed optical communication and imaging fields.

4. APD array detector: using a PN junction doped with high concentration, amplifying the optical signal through avalanche effect. It has the characteristics of high sensitivity, low noise, and fast response, and is suitable for low light level detection and high-speed communication fields.

6、 Operating procedures:

The operating procedures for diode array detectors are as follows:

1. Cleaning: Keep the surface of the diode array detector clean to prevent dust and pollutants from affecting its performance.

2. Power connection: Connect the adapter to the power interface of the diode array detector and ensure stable power supply.

3. Signal input: Input the optical signal into the input port of the diode array detector, which can be connected through optical fiber or directly irradiated.

4. Signal adjustment: Adjust the gain, sensitivity, and other parameters of the diode array detector according to actual needs to achieve the best detection effect.

5. Data acquisition: Through a data acquisition system, the electrical signals output by the diode array detector are converted into digital signals and processed and analyzed accordingly.

6. Data recording: Record the data output by the diode array detector, including information such as light intensity, frequency, time, etc., for subsequent analysis and comparison.

7. Shutdown: After use, promptly turn off the power of the diode array detector and perform appropriate maintenance and upkeep.

7、 Development history:

A diode array detector (DAD) is a commonly used optical detector for analyzing samples in chromatography, spectroscopy, and other analytical instruments.

The development history of diode array detectors can be traced back to the 1970s. Early diode array detectors were composed of a series of serially connected diodes, each corresponding to a certain wavelength of light. These diodes selectively receive light of specific wavelengths through filters and convert photocurrent into voltage signals for detection. This design is simple and highly sensitive, but due to the crosstalk effect between diodes, the linear range of the signal is narrow.

With the development of technology, single-chip diode array detectors emerged in the mid-1980s. This design integrates multiple diodes on a single chip and directly combines the filter with the diodes through microelectronic processing technology, reducing crosstalk effects and improving the linear range and sensitivity of the detector.

In recent years, with the development of nanotechnology, nanostructured diode array detectors have emerged. This design utilizes the special properties of nanomaterials, such as quantum effects and surface plasmon resonance effects, to improve the resolution and sensitivity of the detector.