OPTOELECTRONIC DEVICES

Optoelectronic or optonic devices are systems that detect, generate, control and convert light (photons) into electrical signals (electrons) and vice-versa.

There are several types of optonic devices and they are; light emitting devices (LED), light detecting devices, light modulating devices, light converting devices (photovoltaic), optical communication devices, display technologies and optocouplers/opto-isolators.

Light emitting devices are devices that convert electrical energy into light (electroluminescence), such as light emitting diodes (LEDs), laser diodes (LDs), organic LED (OLEDs), vertical-cavity surface emitting lasers (VCSELs) etc.

Light detecting devices are devices that convert incoming light into electrical current or voltage such as photodiodes, avalanche photodiodes (APDs), photo transistors, charge-coupled devices (CCDs), CMOS image sensors, photomultiplier tubes (PMTs) etc.

Light modulating devices are devices that control or modify light using electrical signals such as electro-optic modulators (EOMs), acousto-optic modulators (AOMs), liquid crystal displays (LCDs), spatial light modulators (SLMs) etc.

Light converting devices (photovoltaic) are devices that convert light energy directly into electrical energy such as solar cells, thermo photovoltaic cells, betavotaics etc.

Optical communication devices are devices that transmit and receive information encoded in light such as optical transceivers, fiber-optics couplers and splitters, wavelength-division multiplexers (WDMs), erbium-doped fiber amplifiers (EDFAs) etc.

Display technologies are devices that convert light into electronic image or displays such as LED, OLED, MicroLED, LCD, E-ink etc. respectively.

Optocouplers/opto-isolators are devices that use light to electrically isolate two circuits while passing a signal between them.

The advantages of optonics devices are; optonics devices operate at frequencies far beyond conventional electronics thus enabling terabit per second communications links. Optonics devices have a wide bandwidth, are energy efficient, for instance LED converts up to 70 to 80% of electrical energy into light compared to just 5% for incandescent bulbs. Optical signals are completely immune to electromagnetic inference (EMI) and radio-frequency interference (RFI). Optonic devices like optocouples allow signal transfer between circuits with no electrical connection, protecting sensitive equipments from voltage spikes, ground loops, and high voltage transients. Modern optonics components can be fabricated at micrometer and nanometer scales enabling compact light weight devices. Optonic devices generate less heat, offer longer lifetimes and inherent physical security advantages over electrical based devices.

The disadvantages of optonic devices are; optonic devices are complex and very expensive to manufacture, sometimes requiring advanced semiconductor fab with tight tolerances, driving costs. Optonic devices are fragile and require precise alignment such that small mechanical vibration or thermal expansion can misalign components and disrupt signals. Optonic devices are sensitive to temperature fluctuations thus requiring active thermal management to relieve thermal stress. Converting between electrical and optical domains introduces latency, power loss and complexity, thus every conversion adds cost and potential failure points. Optonic device signals degrade over distance in free space. Optonic materials are rare, expensive and difficult to integrate with mainstream silicon CMOS processes. Optonic devices like high power lasers and moderate power laser diodes pose serious safety risks.

Optonic devices find applications in the following; optical communication systems, fiber-optics networks and wireless communication systems, laser based surgery, optical imaging and bio sensing applications in medical and health care. Optonio devices find applications in the industry in material processing, laser based manufacturing and optical inspections. Also optonic devices find application in aerospace and defense industry for optical communication systems; laser based sensing and optical navigation. They also find widespread application in consumer electronics such as LED lighting, optical storage (e.g. CD, DVDs) and optical sensing (e.g. gesture recognition).

The future of optonics devices is based on the advances and development of the following technologies; integration of optonics with other technologies like silicon photonics, nano technology and quantum computing.  Advances in material research and semiconductor technologies will result in new and improved optonic devices and systems. Also the future development of compact and portable optonic devices and systems for various applications are expected. The development of more efficient optonic devices and systems for sustainable energy applications like solar energy harvesting will be possible at scale and reduce cost in the process.

 

SOURCES:

• Optoelectronics and photonics: Principles and practices by Safa O. Kasap.
• Optoelectronics: An introduction by John Wilson and John Hawkes.
• Optoelectronics by Emmanuel Rosencher and Borge Vinter.
• Semiconductor optoelectronic devices by Pallab Bhattacharya.
• Optoelectronics by Endel Uiga.