Real-time beam shaping without additional optical elements

Abstract

Providing artificial light and enhancing the quality of the respective light sources is of continued interest in the fields of solid state, condensed matter, and semiconductor physics. Much research has been carried out to increase the luminous efficiency, lifetime and colour stability of such devices. However, the emission characteristics of a given light source do not necessarily comply with today’s often sophisticated applications. Here, beam shaping addresses the transformation of a given light distribution into a customized form. This is typically achieved by secondary optical elements often sporting elaborate designs, where the actual light source takes up only a small fraction of the system’s volume. Such designs limit the final light source to a single permanent operation mode, which can only be overcome by employing mechanically adjustable optical elements. Here we show that organic light-emitting diodes (OLEDs) can enable real-time regulation of a beam shape without relying on secondary optical elements and without using any mechanical adjustment. For a red light-emitting two-unit OLED architecture, we demonstrate the ability to continuously tune between strongly forward and strongly sideward emission, where the device efficiency is maintained at an application-relevant level ranging between 6 and 8% of external quantum efficiency for any chosen setting. In combination with additional optical elements, customizable and tuneable systems are possible, whereby the tuning stems from the light source itself rather than from the use of secondary optics.

84‐3: Invited Paper: Organic Light‐Emitting Diode Beam Shaping: Pixel Design for Variable Angular Emission Profile Control

“…Second, the position of the EML within the cavity and its interaction with the electric field within the device influences both the efficiency and the angular behaviour of the emission. Third, following a Fabry-Pérot resonator behaviour, thicker electrodes lead to a spectrally more confined emission [4,10].…”

“…1 the device architecture is shown. The basic structure is shown on the right hand side and represents an AC/DC OLED [4,5]. This concept is characterised by two independent subunits (OLED 1 and OLED 2) which are stacked on top of each other.…”

“…Having applications like micro displays in mind, particularly bulky beam-shaping structures should be avoided. Only recently we presented an active beam-shaping method, which can exclusively be applied to OLEDs, using their inherent properties, and hence adding nicely to their long list of advantages over alternative light-sources [4]. At that time, we showed a proof-of-concept, discussed upcoming challenges and geometrical influences of such a concept.…”

Directional Polarized Light Emission from Thin‐Film Light‐Emitting Diodes

“…[ 5 ] Controlling the emission profile of a thin‐film LED is desirable for many applications and is referred to as beam‐shaping. [ 6 ] In particular, highly directional beam shapes lead to many interesting applications in solid‐state lighting, [ 7 ] stereoscopic displays, [ 8 ] holographic displays, [ 9 ] optical communication, [ 10,11 ] and integrated lasers. [ 12 ]…”

Narrowband Organic Light‐Emitting Diodes for Fluorescence Microscopy and Calcium Imaging

“…Other, possibly complimentary avenues to narrowing the OLED emission spectrum include the use of more narrow-band emitters such as platinum complexes with a rigid core [47,48] or colloidal quantum dots, [49,50] and applying absorber layers for further spectral filtering. [24,51] Alternatively, shaping the OLED emission profile to have a larger degree of forward direction, e.g., by using photonic structures, [52] micro-lens arrays, [53] or even active steering of the beam direction depending on the objective used, [54] may alleviate the need for filters with a high degree of angular stability.…”