luminous efficacy - university of cagliari · luminous efficacy lm/w 1. lm/w 2....
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Luminous efficacy
Lm/W
1
Lm/W
2
Luminous efficacy (LE)
Lm/W
3
Luminous efficacy (LE)
4
Lab record – CREE303 lum/watt
IKEAPHILIPS
NICHIA
Luminous efficacy (LE)
Fluorescent lighting threshold
DoE
5
Long life up to and beyond 20,000
hours. lifetime –
The energy consumed by one
LED is the equivalent of 50 halogen bulbs.
LEDs offer greater color mixing.
Combined with compact size, offers wide range of design
options.
Compact sizeLong life
Shock resistantInstant on/off
LEDs are more energy efficient.
Coupled with longevity, LED bulbs
= fewer lamps required to be
disposed of.
LOW-COST PERFORMANCE TECHNICAL ENVIRONMENTAL
LED
6
LED
7
°1907 – SiC – yellow emission
1940s: theoretical framework (cfr. transistor, p-n junction)
1955: EL in III-V compounds
1962: IR emission in GaAs (+ laser)
1960s: green and red LEDs based on GaP
Blue: predicted in GaN-based LEDs in 1950sRealized in 1994 – Nobel Prize in 2014
LEDs –
8
LED
9
LED
10
11
White LED GaN or InGaN LED Ce:YAG
12
13
Il Laser
• Caratteristiche• Coerenza• Alta intensita’• Alta direzionalita’• Alta
monocromaticita’
§ Parti principali§ Mezzo attivo§ Metodi di pompaggio§ Cavita’ di risonanza
14
𝐼 = 𝐼!𝑒" #!$#" % Se N2>N1 l'intensità aumenta
𝐼𝐼!= 𝑒"($) 𝐺 𝜈 = 2𝜎 𝑁& − 𝑁' 𝐿
𝛾 𝑓𝑎𝑡𝑡𝑜𝑟𝑒 𝑑𝑖 𝑝𝑒𝑟𝑑𝑖𝑡𝑎𝐼𝐼!= 𝑒" $ () $ 𝐺 > 𝛾 𝑠𝑒 𝑁& − 𝑁' >
𝛾2𝜎𝐿
15
Cavità risonante
𝑛 𝜈 𝑑𝜈 =8𝜋𝜈&
𝑐*Densita’ dei modi di radiazione termica (onde stazionarie in cavita’)
Lo scopo della cavita’ e’ quello di concentrare la radiazione emessa in un numero ridotto di modi in maniera da aumentare il numero di fotoni per ciascuno di tali modi.
G(n)
n16