Lumentum is the main supplier of the Face ID technology in the latest generation of iPhones, and IQE supplies wafers or thin layers of silicon-based material used in making computing chips to the US company.
On Monday, Lumentum cut its fiscal second-quarter sales forecast by 17% at the midpoint, saying a large customer recently reduced its orders for its 3D sensing laser diodes products.
South Korean electronic parts suppliers Samsung Electro-Mechanics Co Ltd, Apple's supplier of multi-layer ceramic capacitors, dropped more than 5 percent, while LG Innotek Co Ltd plunged 9.5 percent.
Following a poor forecast earlier this month, analysts and investors voiced concern over the state of Apple's business, contributing to growing worries that iPhone sales were stagnating and could hurt suppliers.
Apple's iPhone XR might not be the hotseller that analysts had predicted with noted analyst Ming-Chi Kuo slashing shipment forecast for the device.
"Apple could have accumulated too much Lumentum inventory, and needs to work it off, in which case the unit shortfall is less, although it is still indicative of weak iPhone sales".
By Jeran Wittenstein and Mark GurmanIn a world where iPhone demand is on the wane, Apple Inc. has a Plan B. As customers wait longer between upgrades and the smartphone market saturates, Apple can fall back on charging higher prices for each handset and raking in more money from services such as streaming music, digital videos and data storage.
For the first quarter of 2019, January to March, Kuo believes that Apple will see a year-over-year decline in iPhone shipments. In its most-recent quarter, Apple reported nearly no increase in the number of iPhones sold, but revenue from that business jumped 29 percent from a year earlier.
Apple shares fell as much as 5.2 overnight after Lumentum cut its outlook, citing a reduced shipment request from Apple. Jobs, for all his faults, did manage to save Apple with a couple of products which worked - the iPod and iPhone - but even he was running out of ideas before the end (iPads anyone?) and the issue of what to do next was never resolved.
Apple accounted for half of Lumentum's revenue in its December quarter in 2017, while the iPhone is expected to represent 50 percent of Japan Display's revenue this year, according to the Wall Street Journal.
But there's no back-up for numerous companies that supply components for the iPhone.