Dipole nanolaser

FIELD: physics.

SUBSTANCE: dipole nanolaser for generating coherent electromagnetic radiation includes a two-level system in form of a quantum dot and a coherent electromagnetic radiation resonator. The resonator, which has a metal or semiconductor nanoparticle and electrocontact plates, has one more nanoparticle which lies from the said nanoparticle and from the said quantum dot at distances less than wavelength of the coherent electromagnetic radiation generated by the said nanolaser. Both nanoparticles are capable of exciting dipole oscillation modes in antiphase at the frequency of the said coherent electromagnetic radiation.

EFFECT: higher Q-factor of the resonator of the dipole nanolaser.

1 dwg, 1 ex

 

The invention relates to the field of electronic equipment, in particular for the construction and operation of semiconductor lasers, and can be used in systems of recording, reading and information processing.

The level of technology

A known method of generating coherent electromagnetic radiation (hereinafter KAMI) [1], including the pumping energy is placed in the resonator for the electromagnetic field of the active medium to a level when inverted population of energy States of the active medium, i.e. the population of States with higher energy becomes larger than the population of the States of lower energy, and when a certain (threshold) value of naselennosti upper energy States of the radiation of these two systems becomes forced and coherent. It is also known device [2], which implements the above method of generating KAMI - laser heterostructures containing substrate coated with ultra-thin semiconductor layers with geometry of quantum dots placed in the resonator for CAMI, and electro-plate.

The disadvantage of this laser heterostructures is the large size of this cavity, which even in the limit may not be less than the wavelength of KAMI generated by the laser, and is inadequate the narrow width of the spectral line generated CAMI.

Also known dipole nanolaser (DNL) to generate KAMI [3], consisting of quantum dots - a two-level system and a metal or semiconductor nanoparticles with sizes smaller than the wavelength of the specified radiation, placed in a transparent medium at a distance from each other smaller than the wavelength of the specified radiation, which is chosen as the prototype of the present invention.

The disadvantage DNL the prototype is not a high quality of its resonator, the role of which performs the aforementioned nanoparticles excited at a frequency close to the frequency of the localized plasmon resonance (LPR), which complicates the excitation DNL. A significant reason, reducing the quality factor of the specified resonator are energy losses due to radiation of a specified nanoparticles, resonant dipole oscillation mode of which is excited during operation DNL.

The purpose of this invention is to eliminate this drawback and improve the quality factor of the resonator dipole nanolaser.

The objective is achieved due to the fact that the resonator contains an additional one nanoparticle button from the specified nanoparticles and from the specified quantum dots at distances smaller than the wavelength of the coherent electromagnetic radiation for the generation of which is pointed to by the th nanolaser, moreover, these nanoparticles are capable of excitation of the collective dipole oscillation modes, when the dipole moments of the nanoparticles oscillate "out of phase" with each other at the frequency specified coherent electromagnetic radiation, which is close to the natural frequency makers of these nanoparticles.

Description of the invention

The essence of the invention set forth in the following description.

Figure 1 presents a schematic picture of the proposed dipole nanolaser, where

1 - substrate,

2 is a semiconductor cell geometry of quantum dots,

3 is a transparent conductive layer,

4 - metal (or semiconductor) nanoparticles,

5 - transparent conductive layer,

6 - contact plate,

7 - dipole nanolaser.

The proposed dipole nanolaser, works as follows. When applying a potential difference between the substrate (1) and a transparent conductive layer (5) between them, an electric current, by which the electrons in quantum dots (e.g., InGaAs Islands in ultrathin semiconductor layer, for example, from In) fall in the upper energy state of the quantum dots and then relax to their lowest state. Emitted when the quanta of electromagnetic radiation, due to the dipole-dipole interaction between two-level with what Stamou quantum dots and two nanoparticles (for example, spherical, silver), located at a distance smaller than the wavelength of the specified radiation, and having a plasmon resonance frequency close to the frequency of the radiation of a two-tier system, cause in these nanoparticles oscillations of electrons with frequency close to the frequency of the specified radiation, which leads to harmonic oscillations of the dipole moments of these nanoparticles. If geometric shapes and the sizes of these nanoparticles are close enough and they are made of the same material, i.e. if the nanoparticles are almost identical (for example, spherical silver nanoparticles), due to the interaction through the near field can be raised two own fashion oscillations of the electron density (polarization) - "in-phase" and "out of phase".

Note also that the ability to excitation of these modes of oscillation at the resonant frequency have not only identical nanoparticles. This ability to have any two nanoparticles with similar dipole moments, even if they, for example, made of different materials. But because oscillations "in-phase" accompanied by a significant loss of energy by radiation, it lowers the quality factor of the resonator DNL, which role do these two nanoparticles. Also note that the oscillations of a single NAS the particle is always accompanied by a significant loss of energy by radiation, what is a disadvantage of the known nanolaser the prototype.

On the contrary, fashion oscillations "out of phase" has practically no loss of energy to radiation (like it happens in the case of two atoms [4]). Resonance and selective excitation of fashion oscillations "out of phase" means that the frequency of this fashion rebuilt from the frequency of the other fashion, fashion "in phase", the value of the energy of the dipole-dipole interaction of these nanoparticles. When this dipole-dipole interaction between two-level system specified quantum dot and the specified pair of nanoparticles causes a positive feedback between the oscillations of the electrons of these interacting objects, i.e. the larger the amplitude of the dipole moments of these nanoparticles, the higher the probability of transition of an electron between energy States in the two-level system specified quantum dots.

Dipole nanolaser starts working by increasing the potential difference between the substrate (1) and a layer (5), i.e. when increasing the pump rate to such an extent that the population of the upper energy state of the two-level system becomes greater than the population of the lower energy state, i.e. comes inversion States of two-level system, and the rate of radiation of a two-tier system article which becomes more speed radiation losses due to absorption in the metal particle. When these conditions occur coherent radiation in free space at the transition frequency of the two-level system quantum dots close to the frequency of DM nanoparticles.

An example implementation of the present invention

The proposed dipole nanolaser implement, for example, in the technology, such as that described in patent RU 2249278 [3]. Namely, on the substrate (1) (see figure 1) of silicon is grown structure is prefabricated with ultra-thin semiconductor layers (2), for example, from InGaAs.

Then in this structure-the prefabricated method of lateral constraints create elements with geometry of quantum dots, just as is done in [2], where the periodically spaced about 70 nm apart Islands of InGaAs with a diameter of about 30 nm are these quantum dots.

Then this structure of quantum dots on the substrate (1), closes a conductive layer (3), of a thickness of about 10 nm (certainly less than the wavelength specified coherent electromagnetic radiation). After that, the specified conductive layer (3) applied pre-prepared ellipsoidal or spherical silver nanoparticles loved ones sizes and shapes (4) with such density that the average distance between the nanoparticles was less than the length in the wave of the specified CAMI.

Next, the structure of the deposited layer (3) nanoparticles tarasivets conductive material (5), for example gold, transparent (due to the small thickness) for generated KAMI. In many places made of the sample is realized this situation is that at distances smaller than the wavelength of the specified KAMI are a pair of nearly identical nanoparticles, i.e. particles capable of excitation of the dipole oscillations "out of phase". When this mutual arrangement of nanoparticles and quantum dots is smaller than the wavelength of the specified CAMI so that they can form the proposed nanolaser.

To detect these areas, between the substrate (1) and a layer of conductive material (5) potential difference is created, which increases until, when in various parts appears emission KAMI, i.e. starts lasing, CAMI. These places are fixed and are cut from the so prepared sample. On the surface of the cut pieces are put contact plate (6). Each such fragment (7) and is proposed dipole nanolaser.

Sources of information

1. Hkeyi, Manish, Laser heterostructures, World, M., 1976

2. Chelny A.A., Kobyakov MS, Simakov, VA, Elisha p. g, Patent RU 2168249.

3. Simeonova O.A., Protsenko IE, Samoilov V.N., Patent RU 2249278.

4. The percent is about IE, JETP, 103, 167 (2006).

Dipole nanolaser for generating coherent electromagnetic radiation, including a two-tier system in the form of quantum dots, the resonator for coherent electromagnetic radiation, comprising a metal or semiconductor nanoparticles, and the electric contact plate, characterized in that the resonator contains an additional one nanoparticle button from the specified nanoparticles and from the specified quantum dots at distances smaller than the wavelength of the coherent electromagnetic radiation for the generation of which is specified nanolaser, both of these nanoparticles are capable of excitation of the dipole mode oscillations out of phase at the frequency specified coherent electromagnetic radiation.



 

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