Erbium is silver-white metal, soft, insoluble in water, soluble in acid. Salts and oxides are pink to red; melting point 1529°C, boiling point 2863°C, density 9.006g/cm3; erbium is antiferromagnetic at low temperatures, strongly ferromagnetic at near absolute zero, and is a superconductor.
Erbium is slowly oxidized by air and water at room temperature, and erbium oxide is rose red.
Erbium can be used as a reactor control material; Erbium can also be used as an activator for some fluorescent materials. The first ionization energy is 6.10 electron volts. The chemical and physical properties of holmium and dysprosium are almost identical.

Application field
The most prominent use of erbium is in the manufacture of Erbium Dopant Fiber Amplifier (EDFA). Erbium-Doped Fiber Amplifier (EDFA) was first developed by the University of Southampton in England in 1985. It is one of the greatest inventions in optical fiber communication, and it can even be said to be the "gas station" of today's long-distance information highway. Erbium-doped fiber is a silica fiber doped with a small amount of rare earth element erbium ions (Er3+), which is the core of the amplifier. The principle of erbium-doped fiber amplifying optical signal is: when Er3+ is excited by light with wavelength of 980nm or 1480nm and absorbs the energy of pump light, it transitions from the ground state to the pump state of high energy level. Since the lifetime of the particle in the pump state is very short, it is quickly relaxed from the pump state to a metastable state in a non-radiative manner, and the particle has a longer lifetime in this energy and gradually accumulates. When the 1550nm signal light passes through, the metastable Er3+ ions transition to the ground state in the form of stimulated radiation, and also emits light with a wavelength of 1550nm. The light emitted when jumping from the high-energy state to the ground state supplements the signal light lost by the attenuation, so that the signal light can be continuously amplified along with the attenuation during the propagation of the optical fiber.
Doping erbium into an ordinary quartz fiber, coupled with a semiconductor laser with two wavelengths of 980 nm or 1480 nm, basically constitutes an amplifier that directly amplifies the 1550 nm optical signal. Silica fiber can transmit light of different wavelengths, but the light decay rate is different. The light in the 1550nm band transmits the lowest light decay rate (only 0.15 dB/km), and the decay rate is almost the lower limit. Therefore, when the optical fiber communication uses light with a wavelength of 1550 nm as the signal light, the loss of light is minimal. Therefore, as long as tens to hundreds of ppm of erbium are doped in the optical fiber, it can play the role of compensating for the optical loss in the communication system. The erbium-doped fiber amplifier is like an optical "pumping station", which enables the optical signal to be transmitted from station to station without weakening, thus smoothly opening the technical channel of modern long-distance large-capacity high-speed optical fiber communication.
Another hot spot for erbium applications is lasers, especially as medical laser materials. Erbium laser is a solid-state pulsed laser with a wavelength of 2940nm, which can be strongly absorbed by water molecules in human tissue, so that a larger effect can be obtained with a smaller energy, and the soft tissue can be cut, ground and excised very precisely. Erbium YAG lasers are also used for cataract extraction. Because the main component of the cataract lens is water, the erbium laser has low energy and is easily absorbed by water. It will be a promising surgical method for cataract removal. Erbium laser therapy instrument is opening up more and more broad application fields for laser surgery.
Erbium can also be used as an active ion for rare earth upconversion laser materials. Erbium laser up-conversion materials are divided into two categories: single crystal (fluoride, oxygen-containing salt) and glass (fiber), such as erbium-doped yttrium aluminate (YAP:Er3+) crystal and Er3+-doped ZBLAN fluoride (ZrF4- BaF2-LaF3-AlF3-NaF) glass fibers, etc., have now been practical. BaYF5:Yb3+, Er3+ can convert infrared light into visible light, and this multiphoton up-conversion luminescent material has been successfully used in night vision devices.